Background  In the late 1990s, triple reassortant H3N2 influenza A viruses emerged and spread widely in the US swine population. We have shown previously that an isolate representative of this virus-lineage, A/Swine/Minnesota/593/99 (Sw/MN), exhibits phenotypic differences compared to a wholly human-lineage H3N2 virus isolated during the same time period, A/Swine/Ontario/00130/97 (Sw/ONT). Specifically, Sw/MN was more infectious for pigs and infected a significantly higher proportion of cultured primary swine respiratory epithelial cells (SRECs). In addition, reverse genetics-generated Sw/MN × Sw/ONT reassortant and point mutant viruses demonstrated that the infectivity phenotypes in SRECs were strongly dependent on three amino acids within the hemagglutinin (HA) gene.

Objectives  To determine the mechanism by which Sw/MN attains higher infectivity than Sw/ONT in SRECs.

Methods  A/Swine/Minnesota/593/99, Sw/ONT, and mutant (reverse genetics-generated HA reassortant and point mutant) viruses were compared at various HA-mediated stages of infection: initial sialic acid binding, virus entry, and the pH of virus–endosome fusion.

Results/Conclusions  Sialic acid binding was the sole stage where virus differences directly paralleled infectivity phenotypes in SRECs, indicating that binding is the primary mechanism responsible for differences in the infectivity levels of Sw/MN and Sw/ONT.

We report the impact of respiratory viruses on various outbreak settings by using surveillance data from the late first and second wave periods of the 2009 pandemic. A total of 278/345(78·5%) outbreaks tested positive for at least one respiratory virus by multiplex PCR. We detected A(H1N1)pdm09 in 20·6% of all reported outbreaks of which 54·9% were reported by camps, schools, and day cares (CSDs) and 29·6% by long-term care facilities (LCFTs), whereas enterovirus/human rhinovirus (ENT/HRV) accounted for 62% outbreaks of which 83·7% were reported by long-term care facilities (LCTFs). ENT/HRV was frequently identified in LTCF outbreaks involving elderly residents, whereas in CSDs, A(H1N1)pdm09 was primarily detected.

Background  Very little is known regarding the persistence of highly pathogenic avian influenza H5N1 viruses in natural settings during outbreaks in tropical countries, although environmental factors may well play a role in the persistence and in the transmission of H5N1 virus.

Objective  To investigate various environmental compartments surrounding outbreak areas as potential sources for H5N1 virus transmission.

Methods  Environmental specimens were collected following outbreaks of avian influenza in Cambodia between April 2007 and February 2010. The methods used to concentrate H5N1 virus from water samples were based either on agglutination of the virus with chicken red blood cells or on adsorption on glass wool, followed by an elution-concentration step. An elution-concentration method was used for mud specimens. All samples that tested positive by real-time RT-PCRs (qRT-PCRs) targeting the HA5, M and NA1 genes were inoculated into embryonated hen eggs for virus isolation.

Results  Of a total of 246 samples, 46 (19%) tested positive for H5N1 by qRT-PCRs. Viral RNA was frequently detected in dust, mud and soil samples from the farms’ environment (respectively, 46%, 31% and 15%). Samples collected from ponds gave a lower proportion of positive samples (6%) as compared to those collected from the farms (24%). In only one sample, infectious virus particles were successfully isolated.

Conclusion  During H5N1 virus outbreaks, numerous environmental samples surrounding outbreak areas are contaminated by the virus and may act as potential sources for human and/or animal contamination.

Background  The naval experience with the 1918 pandemic during World War I remains underexplored despite its key role on the pandemic’s global diffusion and the epidemiological interest of isolated and relatively homogeneous populations. The pandemic outbreak in the Brazilian naval fleet is of particular interest both because of its severity and the fact that it was the only Latin American military force deployed to war.

Objectives  To study the mortality patterns of the pandemic in the Brazilian fleet sent to patrol the West African coast in 1918.

Method  We investigated mortality across vessels, ranks, and occupations based on official population and mortality records from the Brazilian Navy Archives.

Results  The outbreak that swept this fleet included the highest influenza mortality rate on any naval ship reported to date. Nearly 10% of the crews died, with death rates reaching 13–14% on two destroyers. While overall mortality was lower for officers, stokers and engineer officers were significantly more likely to die from the pandemic, possibly due to the pulmonary damage from constant exposure to the smoke and coal dust from the boilers.

Conclusions  The fatality patterns observed provide valuable data on the conditions that can exacerbate the impact of a pandemic. While the putative lack of exposure to a first pandemic wave may have played a role in the excessive mortality observed in this fleet, our results indicate that strenuous labor conditions, dehydration, and exposure to coal dust were major risk factors. The unequal death rates among vessels remain an open question.

A myriad of risk factors have been linked to an increase in the severity of the pandemic H1N1 2009 influenza A virus [A(H1N1)pdm09] including pregnancy and obesity where death rates can be elevated as compared to the general population. The goal of this review is to provide an overview of the influence of pregnancy and obesity on the reported cases of A(H1N1)pdm09 virus infection and of how the concurrent presence of these factors may have an exacerbating effect on infection outcome. Also, the hypothesized immunologic mechanisms that contribute to A(H1N1)pdm09 virus severity during pregnant or obese states are outlined. Identifying the mechanisms underlying the increased disease severity in these populations may result in improved therapeutic approaches and future pandemic preparedness.

Background  Swine have receptors for both human and avian influenza viruses and are a natural host for influenza A viruses. The 2009 influenza A(H1N1) pandemic (H1N1pdm) virus that was derived from avian, human and swine influenza viruses has infected pigs in various countries.

Objectives  To investigate the relationship between the H1N1pdm viruses isolated from piggery outbreaks in Australia and human samples associated with one of the outbreaks by phylogenetic analysis, and to determine whether there was any reassortment event occurring during the human-pig interspecies transmission.

Methods  Real-time RT-PCR and full genome sequencing were carried out on RNA isolated from nasal swabs and/or virus cultures. Phylogenetic analysis was performed using the Geneious package.

Results  The influenza H1N1pdm outbreaks were detected in three pig farms located in three different states in Australia. Further analysis of the Queensland outbreak led to the identification of two distinct virus strains in the pigs. Two staff working in the same piggery were also infected with the same two strains found in the pigs. Full genome sequence analysis on the viruses isolated from pigs and humans did not identify any reassortment of these H1N1pdm viruses with seasonal or avian influenza A viruses.

Conclusions  This is the first report of swine infected with influenza in Australia and marked the end of the influenza-free era for the Australian swine industry. Although no reassortment was detected in these cases, the ability of these viruses to cross between pigs and humans highlights the importance of monitoring swine for novel influenza infections.

Background  Little is known about the prevalence of viral infections in children with community-acquired pneumonia (CAP).

Objectives  To describe the clinical and virological data collected from children with radiographically confirmed CAP in whom 17 respiratory viruses were sought in respiratory secretion samples during the acute phase of the disease.

Patients and methods  The study involved 592 children with radiographically confirmed CAP whose respiratory secretion samples were tested using the Luminex xTAG Respiratory Virus Panel Fast assay, which simultaneously detects influenza A virus, influenza B virus, respiratory syncytial virus (RSV)-A and -B, parainfluenzavirus-1, -2, -3, and -4, adenovirus, human metapneumovirus, coronaviruses 229E, NL63, OC43, and HKU1, enterovirus/rhinovirus, and bocavirus. A real-time PCR assay was used to identify the rhinovirus in the enterovirus/rhinovirus-positive samples.

Results  A total of 435 children (73·5%) were positive for at least one virus: the most frequently detected was RSV, which was found in 188 (31·7%), followed by rhinovirus (n = 144, 24·3%), bocavirus (n = 60, 10·1%), influenza viruses (n = 57, 9·6), and hMPV (n = 49, 8·2%). Viral co-infections were found in 117 children (19·7% of the enrolled children; 26·9% of those with viral infections). Marginal differences were found between the infections owing to a single virus. Co-infections showed radiographic evidence of alveolar pneumonia significantly more frequently than single infections (OR 1·72, 95% CI 1·05–2·81).

Conclusions  The findings of this study highlight the importance of respiratory viruses (mainly RSV and rhinovirus) in children with CAP and show the characteristics of both the single infections and co-infections associated with the disease.

Background  Nucleoprotein (NP) of influenza viruses is utilized to differentiate between the A, B, and C viral serotypes. The availability of influenza genome sequence data has allowed us to identify specific amino acids at particular positions in viral proteins, including NP, known as “signature residues,” which can be used to discriminate human influenza A viruses from H5N1 highly pathogenic avian influenza in human cases (HPAI) and pandemic H1N1(2009) (H1N1/2009) viruses.

Methods  Screening and epitope mapping of monoclonal antibodies (mAb) against NP of influenza A, which reacted differently with NP from human influenza A virus from HPAI and H1N1/2009 A virus. To identify the epitope(s) responsible for the discrimination of viral NP by mAbs, we prepared mutant NP proteins in the 293 cell expression system because some of the mAbs reacted with non-linear epitopes.

Results and Conclusions  In the present study, we identified 3 mAbs. The results of epitope mapping showed that the epitopes were located at the signature residues. These results indicated that signature residues of NP could discriminate influenza A viruses from different origin.

Background  Large community outbreaks of pandemic A (H1N1) 2009 occurred between October and December 2009 in Mongolia. A serological study was conducted among the general population by testing paired sera collected before and after the first wave of pandemic in Selenghe province, Mongolia. None of the study participants had been vaccinated for pandemic A (H1N1) 2009 before the second samples were collected.

Objective  The objective of this study was to estimate cumulative incidence of pandemic A (H1N1) 2009 in different age-groups of Selenghe province residents.

Methods  After informed consent was obtained from apparently healthy volunteers, the paired sera and background information were collected. Antibody titers were measured using hemagglutinin inhibition (HI) and microneutralization (MN) assays for A/California/07/2009pdm. A fourfold rise in antibody titers was regarded as the evidence of infection.

Results  The overall cumulative incidences in the study group for all ages were 28·8% (76/264) by HI, 35·2% (93/264) by MN, and 25·0% (66/264) by both HI and MN. Cumulative incidences of infection varied among age-groups, with children aged 2–4 and 5–9 years having high cumulative incidence of infection. Overall cumulative incidences of infection in the whole population were estimated to be 23·0% (4946/21 460) by HI, 30·2% (6473/21 460) by MN, and 18·8% (4036/21 460) by both HI and MN.

Conclusions  This study indicates that about one-fourth of the total population in Selenghe province was infected with pandemic A (H1N1) 2009 virus during the first wave of the pandemic.

Background  The recent emergence of the 2009 pandemic influenza A/H1N1 virus has highlighted the value of free and open access to influenza virus genome sequence data integrated with information about other important virus characteristics.

Design  The Influenza Research Database (IRD, http://www.fludb.org) is a free, open, publicly-accessible resource funded by the U.S. National Institute of Allergy and Infectious Diseases through the Bioinformatics Resource Centers program. IRD provides a comprehensive, integrated database and analysis resource for influenza sequence, surveillance, and research data, including user-friendly interfaces for data retrieval, visualization and comparative genomics analysis, together with personal log in-protected ‘workbench’ spaces for saving data sets and analysis results. IRD integrates genomic, proteomic, immune epitope, and surveillance data from a variety of sources, including public databases, computational algorithms, external research groups, and the scientific literature.

Results  To demonstrate the utility of the data and analysis tools available in IRD, two scientific use cases are presented. A comparison of hemagglutinin sequence conservation and epitope coverage information revealed highly conserved protein regions that can be recognized by the human adaptive immune system as possible targets for inducing cross-protective immunity. Phylogenetic and geospatial analysis of sequences from wild bird surveillance samples revealed a possible evolutionary connection between influenza virus from Delaware Bay shorebirds and Alberta ducks.

Conclusions  The IRD provides a wealth of integrated data and information about influenza virus to support research of the genetic determinants dictating virus pathogenicity, host range restriction and transmission, and to facilitate development of vaccines, diagnostics, and therapeutics.

Oseltamivir-resistant 2009 H1N1 influenza virus infections associated with neuraminidase (NA) H275Y have been identified sporadically. Strains possessing the hemagglutinin (HA) D222G mutation have been detected in small numbers of fatal 2009 H1N1 cases. We report the first clinical description of 2009 H1N1 virus infection with both NA-H275Y and HA-D222G mutations detected by pyrosequencing of bronchioalveolar lavage fluid obtained on symptom day 19. The 59-year-old immunosuppressed patient had multiple conditions conferring higher risk of prolonged viral replication and severe illness and died on symptom day 34. Further investigations are needed to determine the significance of infection with strains possessing NA-H275Y and HA-D222G.

Background  The conserved, fusion-active HA2 glycopolypeptide (HA2) subunit of influenza A hemagglutinin comprises four distinct antigenic sites. Monoclonal antibodies (MAbs) recognizing three of these sites are broadly cross-reactive and protective.

Objectives  This study aimed to establish whether antibodies specific to these three antigenic sites were elicited during a natural influenza infection or by vaccination of humans.

Methods  Forty-five paired acute and convalescent sera from individuals with a confirmed influenza A (subtype H3) infection were examined for the presence of HA2-specific antibodies. The fraction of antibodies specific to three particular antigenic sites (designated IIF4, FC12, and CF2 here) was investigated using competitive enzyme immunoassay.

Results  Increased levels of antibodies specific to an ectodomain of HA2 (EHA2: N-terminal residues 23–185 of HA2) were detected in 73% of tested convalescent sera (33/45), while an increased level of antibodies specific to the HA2 fusion peptide (N-terminal residues 1–38) was induced in just 15/45 individuals (33%). Competitive assays confirmed that antibodies specific to the IIF4 epitope (within HA2 residues 125–175) prevailed in 86% (13/15) over those specific to the other two epitopes during infection. However, only a negligible increase in HA2-specific antibodies was detectable following vaccination with a current subunit vaccine.

Conclusions  We observed that the antigenic site localized within N-terminal HA2 residues 125–175 was more immunogenic than that within residues 1–38 (HA2 fusion protein), although both are weak natural immunogens. We suggest that new anti-influenza vaccines should include HA2 (or specific epitopes localized within this glycopolypeptide) to enhance their cross-protective efficacy.

Background  During the early containment phase in England from April to June 2009, the national strategy for H1N1 pandemic influenza involved case investigation and treatment, and tracing and prophylaxis of contacts.

Objective  To describe the relationship between early transmission of H1N1 pandemic influenza in London and age and socio-economic status.

Methods  Epidemiological data on cases of pandemic flu in London reported to the London Flu Response Centre were analysed to determine patterns of transmission.

Results  There were 3487 reported cases (2202 confirmed, 1272 presumed and 14 probable) from 20 April to 28 June 2009, during the ‘containment’ period. The highest report rate of 206 per 100 000 (95% CI 195–218) was seen in primary school–age children (5−11 years) followed by 129 (95% CI 119–139) in secondary school–age children (12–18 years). Reports of cases were initially concentrated in affluent areas but overall showed a clear trend with deprivation and risk ratio of 2·32 (95% CI 1·94–2·78) between the most deprived and the least deprived.

Conclusion  Early transmissions were highest amongst school-aged children but linked with socio-economic deprivation across all age groups.

Background  During the 1918 pandemic period, influenza-related mortality increased worldwide; however, mortality rates varied widely across locations and demographic subgroups. Islands are isolated epidemiological situations that may elucidate why influenza pandemic mortality rates were so variable in apparently similar populations.

Objectives  Our objectives were to determine and compare the patterns of pandemic influenza mortality on islands.

Methods  We reviewed historical records of mortality associated with the 1918–1920 influenza pandemic in various military and civilian groups on islands.

Results and Conclusions  Mortality differed more than 50-fold during pandemic-related epidemics on Pacific islands [range: 0·4% (Hawaii) to 22% (Samoa)], and on some islands, mortality sharply varied among demographic subgroups of island residents such as Saipan: Chamorros [12%] and Caroline Islanders [0·4%]. Among soldiers from island populations who had completed initial military training, influenza-related mortality rates were generally low, for example, Puerto Rico (0·7%) and French Polynesia (0·13%). The findings suggest that among island residents, those who had been exposed to multiple, antigenically diverse respiratory pathogens prior to infection with the 1918 pandemic strain (e.g., less isolated) experienced lower mortality. The continuous circulation of antigenically diverse influenza viruses and other respiratory infectious agents makes widespread high mortality during future influenza pandemics unlikely.

Objectives  To determine the induction and changes in anti-influenza virus secretory IgA (s-IgA) levels in nasal washes and serum IgG levels in patients with influenza.

Methods  The study recruited 16 patients with influenza aged 35·6 ± 9·6 years in 2007/2008 and 2008/2009 seasons. Nasal washes and serum were obtained throughout the first year. Anti-viral s-IgA levels and neutralization activities in nasal washes, and serum anti-viral IgG levels and hemagglutination inhibition (HI) titers were measured.

Results  Anti-viral(H1N1) s-IgA to total IgA ratio and neutralizing antibody titer were low in nasal washes of all patients, whereas serum levels of anti-viral IgG and HI titers varied widely at day 1·4 ± 1·0 postinfection. Both nasal s-IgA and serum IgG levels later increased significantly, reaching peak levels at day 9·6 ± 3·3 postinfection. The induced nasal s-IgA then returned toward the initial levels within 300 days, although the levels at day 143 ± 70 were 3·03-fold of the initial. Individual serum IgG levels also returned toward the initial levels within 300 days, although the mean levels remained high probably because of re-infection in a subgroup of patients. Although influenza A (H3N2) was a minor epidemic subtype in both flu seasons, a significant rise in nasal anti-viral (H3N2) s-IgA levels and a slightly increase in serum IgG levels were noted.

Conclusion  Low levels of nasal anti-viral s-IgA and neutralizing antibody were noted compared with a wide range of serum anti-viral IgG and HI titers at the onset of infection. Elevated s-IgA and IgG returned toward the initial levels within 300 days of infection with minor exceptions.

Surveillance of respiratory viruses has been conducted for many years at the public health laboratory in Hong Kong. With the occurrence of pandemic influenza A (H1N1) 2009, we observed a change in the seasonality of influenza activity with a seemingly corresponding change in the activity of respiratory syncytial virus, parainfluenza virus, and adenovirus during 2009–2011. This phenomenon could most likely be explained by virus interference.

Context  Preventing nosocomial transmission of influenza is essential to reduce the morbidity and mortality associated with this infection. In October 2009, an outbreak of the 2009 influenza A (H1N1) virus occurred in a hematology ward of a children’s hospital over a 21-day period and involved two patients and four healthcare workers.

Objective  To investigate nosocomial transmission of the 2009 influenza A (H1N1) virus in patients and healthcare workers.

Design, setting, and participants  An outbreak investigation was initiated in response to suspected nosocomial transmission of the 2009 influenza A (H1N1) virus during the peak of the 2009 pandemic. Cases were confirmed using a polymerase chain reaction (PCR) test specific for the 2009 H1N1 influenza A virus. Viruses isolated from nasopharyngeal swabs were genetically characterized using Sanger sequencing of uncloned “bulk” PCR products.

Main outcome measures  Virus sequencing to investigate nosocomial transmission.

Results  Two immunocompromised patients and four healthcare workers were found to be part of a nosocomial outbreak of the 2009 influenza A (H1N1) virus. One immunocompromised patient had a second episode of clinical influenza infection after isolation precautions had been discontinued, resulting in additional exposures. Strain-specific PCR showed that all cases were caused by infection of the 2009 H1N1 virus. Sequencing of viral genes encoding hemagglutinin and polymerase basic subunit 2 (PB2) revealed that all viruses isolated were genetically identical at these loci, including the two episodes occurring in the same immunocompromised patient.

Conclusions  Prompt institution of isolation precautions is essential in preventing nosocomial outbreaks of the 2009 novel influenza A (H1N1) virus. Our data suggest that isolation precautions may need to be continued for a prolonged period of time in immunocompromised patients with influenza infection.

Background  In the post-pandemic period, pandemic (H1N1) 2009 virus was expected to circulate seasonally and was introduced into trivalent influenza vaccine during 2010/2011 season in the Northern Hemisphere.

Objectives  The aim of this study was to examine the evolution of herd immunity against pandemic (H1N1) 2009 virus in Beijing, China, during 2010/2011 season and effectiveness of the 2010/2011 trivalent vaccine.

Methods  Two serological surveys were conducted before and after 2010/2011 season in Beijing. A case–control study was used to investigate vaccine effectiveness against influenza-like illness (ILI) and lower respiratory tract infection (LRI).

Results  A total of 4509 and 4543 subjects participated in the pre- and post-season surveys, respectively. The standardized seroprevalence of pandemic (H1N1) 2009 influenza increased from 22·1% pre-season to 24·3% post-season (P < 0·001). Significant elevation in seroprevalence appeared in the ≥60 years age-group (P < 0·001), but not in others. The 2010/2011 trivalent vaccine contributed to the higher post-seasonal seroprevalence in unvaccinated individuals (P = 0·024), but not in those vaccinated with monovalent pandemic vaccine (P = 0·205), as well as in those without prior immunity versus those with immunity. The adjusted effectiveness of the 2010/2011 trivalent vaccine was 79% protection against ILI (95% CI, 61–89%) and 95% against LRI (95% CI: 59–99%).

Conclusions  A slight increase in herd immunity against pandemic (H1N1) 2009 influenza was observed in Beijing, China, during the 2010/2011 season. Prior vaccination and immunity had a suppressive impact on immune response toward this novel influenza virus, elicited by 2010/2011 trivalent vaccine. This trivalent vaccine conferred good protection against ILI and LRI.

Background  Transmission of highly pathogenic avian influenza and the recent pandemic H1N1 viruses to domestic cats and other felids creates concern because of the morbidity and mortality associated with human infections as well as disease in the infected animals. Experimental infections have demonstrated transmission of influenza viruses in cats.

Objectives  An epidemiologic survey of feral cats was conducted to determine their exposure to influenza A virus.

Methods  Feral cat sera and oropharyngeal and rectal swabs were collected from November 2008 through July 2010 in Alachua County, FL and were tested for evidence of influenza A virus infection by virus isolation, PCR, and serological assay.

Results and conclusions  No virus was isolated from any of 927 cats examined using MDCK cell or embryonated chicken egg culture methods, nor was viral RNA detected by RT-PCR in 200 samples tested. However, 0.43% of cats tested antibody positive for influenza A by commercial ELISA. These results suggest feral cats in this region are at minimal risk for influenza A virus infection.

Background  The pandemic of 2009 was caused by an H1N1 (H1N1pdm) virus of swine origin. This pandemic virus has repeatedly infected swine through reverse zoonosis, although the extent of such infection in swine remains unclear.

Objective  This study targets small and commercial pig producers in North Vietnam, in order to estimate the extent of H1N1pdm infection in swine and to identify the risk factors of infection.

Methods  Virologic and serologic surveillance of swine was carried out in 2009–2010 in pig farms (38 swabs and 1732 sera) and at a pig slaughterhouse (710 swabs and 459 sera) in North Vietnam. The sera were screened using a influenza type A-reactive ELISA assay, and positive sera were tested using hemagglutination inhibition tests for antibody to a panel of H1-subtype viruses representing pandemic (H1N1) 2009 (H1N1pdm), triple reassortant (TRIG), classical swine (CS), and Eurasian avian-like (EA) swine lineages. Farm-level risk factors were identified using a zero-inflated negative binomial model.

Results  We found a maximal seroprevalence of H1N1pdm of 55·6% [95% CI: 38·1–72·1] in the slaughterhouse at the end of December 2009, 2 weeks after the peak of reported human fatalities with H1N1pdm. Farm-level seroprevalence was 29% [95% CI: 23·2–35·7]. In seropositive farms, within-herd seroprevalence ranged from 10 to 100%. We identified an increased risk of infection for farms that specialized in fattening and a decreased risk of infection in farms hiring external swine workers.

Conclusions  Our findings suggest extensive reverse-zoonotic transmission from humans to pigs with subsequent onward transmission within pig herds.

Background  Since 2004, the Naval Health Research Center, with San Diego and Imperial counties, has collaborated with the US Centers for Disease Control and Prevention to conduct respiratory disease surveillance in the US-Mexico border region. In 2007, the Secretariat of Health, Mexico and the Institute of Public Health of Baja California joined the collaboration.

Objectives  The identification of circulating respiratory pathogens in respiratory specimens from patients with influenza-like illness (ILI).

Methods  Demographic, symptom information and respiratory swabs were collected from enrollees who met the case definition for ILI. Specimens underwent PCR testing and culture in virology and bacteriology.

Results  From 2004 through 2009, 1855 persons were sampled. Overall, 36% of the participants had a pathogen identified. The most frequent pathogen was influenza (25%), with those aged 6–15 years the most frequently affected. In April 2009, a young female participant from Imperial County, California, was among the first documented cases of 2009 H1N1. Additional pathogens included influenza B, adenovirus, parainfluenza virus, respiratory syncytial virus, enterovirus, herpes simplex virus, Streptococcus pneumoniae, and Streptococcus pyogenes.

Conclusions  The US-Mexico border is one of the busiest in the world, with a large number of daily crossings. Due to its traffic, this area is an ideal location for surveillance sites. We identified a pathogen in 36% of the specimens tested, with influenza A the most common pathogen. A number of other viral and bacterial respiratory pathogens were identified. An understanding of the incidence of respiratory pathogens in border populations is useful for development of regional vaccination and disease prevention responses.

Background  In 1997, highly pathogenic avian influenza (HPAI) viruses caused outbreaks of disease in domestic poultry markets in Hong Kong. The virus has also been detected in infected poultry in Europe and Africa.

Objective  The objective of this study was to determine the efficacy of a heterologous vaccine administered with and without the aluminum hydroxide adjuvant in ferrets challenged with HPAI (A/Vietnam/1203/04).

Methods  Animals in four of the five groups were vaccinated twice 21 days apart, with two doses of a heterologous monovalent subvirion vaccine with or without an aluminum hydroxide adjuvant and challenged with a lethal target dose of A/Vietnam/1203/04.

Results  All animals vaccinated with the heterologous vaccine in combination with the aluminum hydroxide adjuvant survived a lethal challenge of A/Vietnam/1203/04. Four of the eight animals vaccinated with 30 μg of the vaccine without the adjuvant survived, while two of the eight animals vaccinated with 15 μg of the vaccine without the adjuvant survived. None of the unvaccinated control animals survived challenge. Additionally, changes in virus recovered from nasal washes and post-mortem tissues and serology suggest vaccine efficacy.

Conclusions  Altogether, the data suggest that the heterologous vaccine in combination with the aluminum hydroxide adjuvant offers maximum protection against challenge with A/Vietnam/1203/04 when compared to the unvaccinated control animals or animals vaccinated without any adjuvant.

There are limited data on the use of masks and respirators to reduce transmission of influenza. A systematic review was undertaken to help inform pandemic influenza guidance in the United Kingdom. The initial review was performed in November 2009 and updated in June 2010 and January 2011. Inclusion criteria included randomised controlled trials and quasi-experimental and observational studies of humans published in English with an outcome of laboratory-confirmed or clinically-diagnosed influenza and other viral respiratory infections. There were 17 eligible studies. Six of eight randomised controlled trials found no significant differences between control and intervention groups (masks with or without hand hygiene; N95/P2 respirators). One household trial found that mask wearing coupled with hand sanitiser use reduced secondary transmission of upper respiratory infection/influenza-like illness/laboratory-confirmed influenza compared with education; hand sanitiser alone resulted in no reduction. One hospital-based trial found a lower rate of clinical respiratory illness associated with non-fit-tested N95 respirator use compared with medical masks. Eight of nine retrospective observational studies found that mask and/or respirator use was independently associated with a reduced risk of severe acute respiratory syndrome (SARS). Findings, however, may not be applicable to influenza and many studies were suboptimal. None of the studies established a conclusive relationship between mask/respirator use and protection against influenza infection. Some evidence suggests that mask use is best undertaken as part of a package of personal protection especially hand hygiene. The effectiveness of masks and respirators is likely linked to early, consistent and correct usage.

Background  The mass media is a key component of any public communication strategy for influenza or other respiratory illnesses, but coverage can be variable. In this study, we explored the factors that influenced journalists’ coverage of avian influenza as a model for coverage of a potential influenza pandemic.

Methods  This study involved semi-structured interviews with 16 journalists from major Australian print, radio and television media organisations reporting on avian influenza and pandemic planning. Journalists, including reporters, editors and producers, were interviewed between October 2006 and August 2007. Thematic analysis was used to draw out major lessons for health communicators.

Results  Coverage of avian influenza was influenced by a small set of news values: catastrophic potential, cultural and geographical proximity, unfamiliarity and uncertainty. Lack of novelty and the absence of compelling images led to a decline in coverage. Journalists expressed concerns about the accuracy and impacts of reporting, but saw as critically important, their primary role as informants. They hence emphasised the importance of journalistic independence. Journalists all intended to continue working in a pandemic.

Conclusions  Health experts need to adapt their timetables and resources to journalists’ needs to improve their mutual communication. In crisis situations, journalists communicate with the public efficiently and effectively, but expert and journalistic views on the role and content of coverage may diverge in the post-acute, reflective phase of a crisis.

The 2009 influenza A/H1N1 pandemic caused an increase in complications in pregnant women. To be well prepared for a next pandemic, we investigated the obstetric and maternal complications of this pandemic. In our national cohort of 59 pregnant women who were admitted to the hospital, no major complications apart from preterm birth and admission to the neonatal intensive care unit were observed. Although the small size of this study precludes us drawing any definitive conclusions, comparing our results with those in other countries suggests that the influenza A/H1N1 pandemic had a relatively benign course in pregnant women in The Netherlands.

Background  Avian influenza viruses (AIV) have been detected in wild birds in West Africa during the northern winter, but no information is available on a potential year-round circulation of AIV in West Africa. Such year-round circulation would allow reassortment opportunities between strains circulating in Afro-tropical birds and strains imported by migratory birds wintering in West Africa.

Objective and Method  A 2-year longitudinal survey was conducted in the largest continental wetland of West Africa, the Inner Niger Delta in Mali, to determine the year-round circulation of AIV in wild birds.

Results and Conclusions  Avian influenza virus RNA was detected during all periods of the year. Very low prevalence was detected during the absence of the migratory wild birds. However, a year-round circulation of AIV seems possible in West Africa, as shown in other African regions. West Africa may hence be another potential site of reassortment between AIV strains originating from both Afro-tropical and Eurasian regions.

Background  Evaluation of two commercial lateral flow devices (LFDs) for avian influenza (AI) detection in H5N1 highly pathogenic AI infected poultry in Vietnam.

Objectives  Determine sensitivity and specificity of the LFDs relative to a validated highly sensitive H5 RRT PCR.

Methods  Swabs (cloacal and tracheal) and feathers were collected from 46 chickens and 48 ducks (282 clinical specimens) and tested by both LFDs and H5 RRT PCR. A subset of 59 chicken and 34 duck specimens was also tested by virus isolation (VI), the ‘gold standard’.

Results  Twenty-six chickens and 15 ducks were shown to be infected by at least one RRT PCR positive clinical specimen per bird. Bird-level sensitivity for the Anigen LFD was 84·6% for chickens and 53·3% for ducks, and for the Quickvue LFD 65·4% for chickens and 33·3% for ducks. Comparison of the three clinical specimens revealed that chicken feathers were the most sensitive with 84% and 56% sensitivities for Anigen and Quickvue respectively. All 21 RRT PCR positive swabs from ducks were negative by both LFDs. However, duck feather testing gave sensitivities of 53·3% and 33·3% for Anigen and Quickvue respectively. Specificity was 100% for both LFDs in all investigations.

Conclusions  Although LFDs were less sensitive than AI RRT PCR and VI, high titre viral shedding in H5N1 highly pathogenic avian influenza (HPAI) infected and diseased chickens is sufficient for a proportion of birds to be identified as AI infected by LFDs. Feathers were the optimal specimen for LFD testing in such diseased HPAI scenarios, particularly for ducks where swab testing by LFDs failed to identify any infected birds. However, specimens should be forwarded to the laboratory for confirmation by more sensitive diagnostic techniques.

Objective  Given their medical vulnerabilities, we investigated the epidemiological factors related to H1N1 infection in school-aged children.

Methods  This study analyzed data collected on 7448 school-aged children in South Korea between 18 November and 8 December 2009.

Results  We found that H1N1 infection was associated with body mass index (BMI), waist circumference (WC), the use of facemasks, contact history with H1N1-infected persons, and overseas travel history (P < 0·05). In addition, WC quartiles were significantly associated with H1N1 infection after adjusting for BMI and other confounding variables [OR (95% CI): 1·00, 1·10 (0·72–1·45), 1·13 (0·76–1·67), and 2·71 (1·74–4·24), respectively).

Conclusions  Abdominal obesity and the use of facemasks appear to be independently associated with H1N1 infection in school-aged children. We infer that providing education on wearing facemasks and specific planning for abdominally obese children and adolescents may be effective means of reducing the spread of the influenza pandemic in school-aged children.

Purulent bronchitis was a distinctive and apparently new lethal respiratory infection in British and American soldiers during the First World War. Mortality records suggest that purulent bronchitis caused localized outbreaks in the midst of a broad epidemic wave of lethal respiratory illness in 1916–1917. Probable purulent bronchitis deaths in the Australian Army showed an epidemic wave that moved from France to England. Purulent bronchitis may have been the clinical expression of infection with a novel influenza virus which also could have been a direct precursor of the 1918 pandemic strain.

Nineteen patients with oseltamivir-resistant seasonal influenza A (H1N1) infections were randomized to receive oseltamivir or placebo. Nasopharyngeal swabs were obtained, and clinical and virologic outcomes were compared, stratified by early or late treatment. Neuraminidase inhibition assay and pyrosequencing for H275Y confirmed resistance. Twelve (63%) patients received oseltamivir; 8 (67%) received late treatment. Seven (37%) patients received placebo; 6 (86%) presented >48 hours after onset. Time to 50% decrease in symptom severity, complete symptom resolution, and first negative culture were shortest among the early treatment group. While sample size prohibits a strong conclusion, future studies should evaluate for similar trends.

Background  An influenza outbreak might result in disruption of services at acute care setting hospitals.

Objectives  In this study, we retrospectively evaluated the use of neuraminidase inhibitor chemoprophylaxis for prevention of nosocomial spread of influenza in a university hospital.

Patients/Methods  During the 3-year study period, 202 index cases of influenza [30 hospitalized patients and 172 healthcare workers (HCW)] and 762 individuals who had had close contact with the index cases (248 hospitalized patients and 514 HCW) were identified. Of these contacts, 416 received neuraminidase inhibitor chemoprophylaxis.

Results  When both the index cases and the close contacts were hospitalized patients, the incidence of influenza was lower among the close contacts who received chemoprophylaxis than among those who did not (odds ratio, 0·07; confidence interval, 0·01–0·49; P = 0·012). In contrast, when the index cases were HCW, the incidence of influenza was not different between close contacts who did or did not receive chemoprophylaxis.

Conclusions  This study suggests that chemoprophylaxis might be useful to prevent nosocomial spread of infection between hospitalized patients.

Background  Quantitative knowledge of the transmissibility of influenza is crucial to its prevention and control.

Objectives  To quantify the transmission of influenza A (H1N1) and seasonal influenza in household contacts of patients with influenza diagnosed in a large university hospital.

Patients/Methods  A prospective study was conducted between September and October 2009 in which all confirmed cases of influenza diagnosed at King Khalid University Hospital were included. All household contacts were followed by telephone calls every other day for 12 days. They were asked about the development of influenza symptoms in addition to their age and nationality.

Results  Overall, 432 household contacts of 69 influenza A (H1N1) cases and 417 contacts of 91 seasonal influenza cases were included. Suspected influenza was diagnosed in 16·9% and 14·4% of household contacts of H1N1 and seasonal influenza patients, respectively. Household reproduction numbers were 1·06 (0·84–1·28) for H1N1 and 0·66 (0·51–0·81) for seasonal influenza. Children in households were more susceptible than were adults (22·2% versus 13·7%, respectively). Evidence of coughing in the index case tripled the risk of infection in households afflicted with the H1N1 influenza [relative risk (RR) = 3·28, CI = 1·24–8·69], while evidence of a runny nose doubled it (RR = 1·89, CI = 1·19–2·92).

Conclusions  Communicability of influenza in households in Riyadh is comparable to that in other countries. Children are more susceptible to influenza infection. The presence of a cough or runny nose in the index cases increases the risk of infection.

Background  Starting with the 2010–2011 influenza season, the Advisory Committee on Immunization Practices at the US Centers for Disease Control and Prevention recommends annual influenza vaccination to all people aged 6 months and older unless contraindicated.

Objectives  To measure perceived influenza vaccination recommendation status among US adults (n = 2122) and its association with socio-demographic characteristics and recommendation status during the 2009–2010 pandemic influenza season.

Methods  We analyze nationally representative data from longitudinal Internet surveys of US adults conducted in November–December 2009 and September–October 2010.

Results  During the 2010–2011 vaccination season, 46·2 percent (95%-CI: 43·3–49·1%) of US adults correctly reported to be covered by a government recommendation for influenza vaccination. Awareness of being covered by a government influenza vaccination recommendation was statistically significantly higher among non-working adults and adults who had been recommended for seasonal vaccination or both seasonal and H1N1 vaccination during the 2009–2010 pandemic influenza vaccination season.

Conclusion  Our results highlight that a majority of US adults do not know that they are recommended for annual influenza vaccination by the government. The fraction of adults who are unaware of their recommendation status is especially large among newly recommended healthy young adults. The universal vaccination recommendations will only be successful if they reach both patients and physicians and lead to changing vaccination practices. The universal nature of the new recommendation simplifies vaccination-related outreach and compliance with government vaccination guidelines considerably, as it does not require any identification of specific recommendation groups based on complex personal or health risk factors.

Background  The performance of rapid influenza diagnostic tests (RIDTs) in detecting influenza A(H1N1) 2009 has varied widely. Evaluations of RIDTs among infected individuals across all age groups have not been described in depth.

Objectives  Determine RIDT clinical sensitivity in comparison with influenza detection using real-time RT-PCR among patients infected with influenza A(H1N1) 2009 across all age groups.

Study design  This study analyzed respiratory specimens received by the New Hampshire Public Health Laboratories (NHPHL) from September 1, 2009, through December 31, 2009. RIDT performance was evaluated among different age groups of patients determined to be infected with influenza A (H1N1) 2009, and the association between age and RIDT sensitivity was determined.

Results  Of 1373 specimens examined, 269 tested positive for influenza A(H1N1) 2009 by real-time RT-PCR (rRT-PCR) and had RIDT results available. Overall clinical sensitivity and specificity of RIDTs were 53·9 and 98·5%, respectively. By age group, clinical sensitivity was 85·7% in patients <2 years old, 60·3% in patients between 2- and 39 years old, and 33·3% in patients aged 40 and older. Logistic regression analysis indicated that increasing age was negatively associated with RIDT performance.

Conclusion  Rapid influenza diagnostic test sensitivity decreased significantly with increasing age. Findings from this study may impact a clinician’s interpretation of RIDT test results and ultimately have implications in clinical decision-making.

Background  Point of care tests (POCTs) for influenza potentially offer earlier diagnosis, enabling specific treatment, infection control measures and greater patient convenience and satisfaction. Current POCTs have limited sensitivity, some cannot distinguish influenza types, none differentiate subtypes and are relatively expensive.

Aims  To identify and characterise influenza POCTs expected to be available for clinical use in the UK by mid-2013, highlighting those with potential benefits over existing tests.

Methods  Potential developers of influenza POCTs were identified through known manufacturers’ websites, Medical Technology trade associations, the EuroScan International Network, an expert advisory group and by searching relevant online sources. Identified companies were asked to provide standard information on relevant technologies.

Results  Fifty-six companies were identified, and 29 (52%) responded, identifying 57 potentially relevant technologies. Of these, 40 (70%) were already available or had undetermined status and 5 (9%) were excluded as time to results took over 60 minutes. Of the remaining 12 emerging POCTs, 10 (83%) reportedly enabled differentiation of influenza types and eight differentiation of A subtypes. Nasopharyngeal swabs were the most commonly acceptable sample type; the sample volume ranging from 80 μl to 1·4 ml.

Discussion  Most identified emerging influenza POCTs offered differentiation of influenza type and subtype. Tests claiming this capability include several incorporating reverse transcription polymerase chain reaction assays; though, these also had the longest time to result. However, whilst some identified POCTs exhibit high sensitivity and specificity, most lack published clinical data for assessment, and the overall costs of these technologies remains largely unknown.

Influenza neuraminidase is the target of two licensed antivirals that have been very successful, with several more in development. However, neuraminidase has been largely ignored as a vaccine target despite evidence that inclusion of neuraminidase in the subunit vaccine gives increased protection. This article describes current knowledge on the structure, enzyme activity, and antigenic significance of neuraminidase.

Analysis of a US hospitalization database demonstrated that more influenza patients were hospitalized and the age distribution of hospitalizations was younger during the 2009 (H1N1) influenza A pandemic compared with the three previous influenza seasons. The duration of hospital stay remained stable in all four seasons. A higher proportion of patients was treated with antivirals (P < 0·0001), comprised almost entirely of neuraminidase inhibitors, and the proportion was highest in those with influenza confirmed by diagnostic testing (P < 0·0001). Approximately one-third remained untreated. Young children had the lowest rate of neuraminidase-inhibitor treatment during the 2009 pandemic (P < 0·05).

There is no national estimate of adult influenza vaccination by US office-based pediatricians. De-identified patient-level data from an electronic healthcare claims database submitted to private and public insurers were analyzed for pediatric offices from the 2006–2007 through 2010–2011 seasons. An average of 321 000 (range: 225 000–434 000) influenza vaccinations per year were estimated to be administered to adults; 52%, 22%, and 26% were given to adults 19–49, 50–64, and ≥65 years of age, respectively. Consistent with the 2010 changes to national guidelines, recommending influenza vaccination of all individuals 6 months of age and older, pediatricians appear to be providing an increasing proportion of adult vaccinations against influenza to adults 19–49 years of age (probably parents of their pediatric patients).

Background  The re-emergence of avian influenza A (H5N1) in 2004 and the pandemic of influenza A (H1N1) in 2009 highlight the need for routine surveillance systems to monitor influenza viruses, particularly in Southeast Asia where H5N1 is endemic in poultry. In 2004, the Thai National Institute of Health, in collaboration with the US Centers for Disease Control and Prevention, established influenza sentinel surveillance throughout Thailand.

Objectives  To review routine epidemiologic and virologic surveillance for influenza viruses for public health action.

Methods  Throat swabs from persons with influenza-like illness and severe acute respiratory illness were collected at 11 sentinel sites during 2004–2010. Influenza viruses were identified using the standard protocol for polymerase chain reaction. Viruses were cultured and identified by immunofluorescence assay; strains were identified by hemagglutination inhibition assay. Data were analyzed to describe frequency, seasonality, and distribution of circulating strains.

Results  Of the 19 457 throat swabs, 3967 (20%) were positive for influenza viruses: 2663 (67%) were influenza A and able to be subtyped [21% H1N1, 25% H3N2, 21% pandemic (pdm) H1N1] and 1304 (33%) were influenza B. During 2009–2010, the surveillance system detected three waves of pdm H1N1. Influenza annually presents two peaks, a major peak during the rainy season (June–August) and a minor peak in winter (October–February).

Conclusions  These data suggest that March–April may be the most appropriate months for seasonal influenza vaccination in Thailand. This system provides a robust profile of the epidemiology of influenza viruses in Thailand and has proven useful for public health planning.

Background  Recent studies have demonstrated that rapid influenza diagnostic tests (RIDTs) have a relatively low sensitivity in detecting severe cases of pandemic H1N1 2009 influenza virus (pH1N1) infection. We hypothesized that viral load in upper respiratory specimens obtained on presentation may not be correlated with disease severity.

Methods  We conducted a prospective study to compare patterns of viral shedding using nasopharyngeal swab specimens, according to the number of days of post-symptom onset and post-antiviral therapy, between patients with and without complications.

Results  From July 15, 2009 through July 23, 2010, we collected and processed a total of 141 nasopharyngeal swab specimens from 64 inpatients and outpatients with laboratory-confirmed pH1N1 infection. These included 46 patients without any complications (uncomplicated group) and 18 patients who required hospital admission (complicated group). The mean initial viral load was higher in the uncomplicated group than in the complicated group (3·4 ± 1·6 log₁₀ copies/μl versus 1·9 ± 1·7, P = 0·02). However, prolonged viral shedding was only detected in the complicated group (44% by day 7 of antiviral therapy). By multivariate analysis, we found that age (OR, 1·1; 95% CI, 1·0–1·1) and initial nasopharyngeal viral load (OR, 0·5; 95% CI, 0·3–0·8) were significant factors associated with complications.

Conclusion  Given that patients with severe pH1N1 infection may have relatively lower initial viral load in the upper respiratory tract, cautious interpretation of negative RIDT results is particularly warranted in this patient population.

Background  Shared seasonal patterns, such as between influenza and some respiratory bacterial infections, can create associations between phenomena not causally related.

Objectives  To estimate the association of influenza with subsequent bacterial infections after full adjustment for confounding by seasonal and long-term trends.

Methods  Time series of weekly counts of notified cases of invasive infections with Haemophilus influenzae, Neisseria meningitidis, Streptococcus pneumoniae and Streptococcus pyogenes, in Montréal, Canada, 1996–2008, were modelled by negative binomial regression, with terms representing seasonal and long-term trends and terms for numbers of positive laboratory tests for influenza A and B.

Results  The associations of S. pneumoniae, H. influenzae and N. meningitidis with influenza disappeared after seasonal terms were added to the model. However, the influenza B count remained associated with the S. pyogenes counts for the same week and the following week: S. pyogenes incidence rate ratios were 1.0376 (95% CI: 1.0009–1.0757) and 1.0354 (0.9958–1.0766), respectively, for each increase of 1 in the influenza count.

Conclusions  Influenza B accounts for about 8percnt; of the incidence of invasive S. pyogenes infections, over and above any effect associated with modellable seasonal and long-term trends. This association of influenza B with S. pyogenes infections can be attributed largely to the years 1997, 2001, 2007 and 2008, when late peaks in influenza B counts were followed by peaks in S. pyogenes notifications. This finding reinforces the case for universal immunization against influenza, as partial protection against the ‘flesh eating disease’.

Objectives  Influenza can be a serious illness, especially for older people, and reducing the impact of influenza in elderly is important. The objective of this study was to estimate the prevalence and postinfection outcomes of influenza among the over-50 population in Japan.

Design  An observational study was designed to ascertain the proportion of influenza cases in a population aged ≥50 years with acute respiratory infection (ARI) and to determine the postinfection outcomes of their illness during the 2008–09 influenza season in Japan. Respiratory specimens obtained from a total of 401 patients were tested by PCR for influenza viruses, respiratory syncytial virus (RSV) and human metapneumovirus (hMPV). The effectiveness of the seasonal trivalent influenza vaccine was estimated by a test-negative case control analysis.

Setting  Seventeen outpatient clinics located in four separate areas of Japan.

Sample  Respiratory swab specimens from the ARI patients aged ≥50 years.

Main outcome measures  Laboratory confirmed influenza in patients presenting with ARI.

Results  In all, 89 (22.2%) of the patients were positive for one of the tested viruses; 70 (78.7%) with influenza, 17 (19.1%) with RSV, and 2 (2.2%) with hMPV. Cough (95.7% vs 73.4%), loss of appetite (67.1% vs 35.5%), absence from work (50.0% vs 23.0%), impact on daily activity (90.0% vs 62.5%), and caregiver absence from work (5.7% vs 0.6%) were observed higher in influenza patients. The duration of feeling weakness (6.3 ± 5.4 vs 3.6 ± 1.9 days) and average days of reduced activity (5.2 vs 3.6 days) were longer for influenza patients. Vaccine effectiveness was estimated to be 32.1% (95% CI: −14.9, 59.9%).

Conclusions  Influenza was the dominant ARI-causing virus and the clinical and socio-economic outcomes imposed on patients over 50 years of age was high for influenza.

Background  Influenza virus is a globally important respiratory pathogen that causes a high degree of annual morbidity and mortality. Significant antigenic drift results in emergence of new, potentially pandemic, virus variants. The best prophylactic option for controlling emerging virus strains is to manufacture and administer pandemic vaccines in sufficient quantities and to do so in a timely manner without impacting the regular seasonal influenza vaccine capacity. Current, egg-based, influenza vaccine production is well established and provides an effective product, but has limited capacity and speed.

Objectives  To satisfy the additional global demand for emerging influenza vaccines, high-performance cost-effective technologies need to be developed. Plants have a potential as an economic and efficient large-scale production platform for vaccine antigens.

Methods  In this study, a plant virus-based transient expression system was used to produce hemagglutinin (HA) proteins from the three vaccine strains used during the 2008–2009 influenza season, A/Brisbane/59/07 (H1N1), A/Brisbane/10/07 (H3N2), and B/Florida/4/06, as well as from the recently emerged novel H1N1 influenza A virus, A/California/04/09.

Results  The recombinant plant-based HA proteins were engineered and produced in Nicotiana benthamiana plants within 2 months of obtaining the genetic sequences specific to each virus strain. These antigens expressed at the rate of 400–1300 mg/kg of fresh leaf tissue, with >70% solubility. Immunization of mice with these HA antigens induced serum anti-HA IgG and hemagglutination inhibition antibody responses at the levels considered protective against these virus infections.

Conclusions  These results demonstrate the feasibility of our transient plant expression system for the rapid production of influenza vaccine antigens.

Background  Guillain–Barre syndrome (GBS) is a rare autoimmune disease characterized by acute, progressive peripheral neuropathy and is commonly associated with the presence of antiganglioside antibodies. Previously, influenza vaccination was linked with the increased incidence of GBS; however, whether antiganglioside antibodies are subsequently induced remains unresolved.

Methods  Sera from human subjects vaccinated with seasonal influenza vaccines from the 2007–2008, 2008–2009, or 1976–1977 influenza seasons were screened for the induction of immunity to influenza and the presence of antiganglioside antibodies pre- and post-vaccination. Likewise, sera from mice vaccinated with seasonal influenza vaccines (1988–1989, 2007–2008) or “swine flu” pandemic vaccines (1976, 2009) were assessed in the same manner. Viruses were also screened for cross-reacting ganglioside epitopes.

Results  Antiganglioside antibodies were found to recognize influenza viruses; this reactivity correlated with virus glycosylation. Antibodies to influenza viruses were detected in human and mouse sera, but the prevalence of antiganglioside antibodies was extremely low.

Conclusions  Although the correlation between antiganglioside antibody cross-reactivity and glycosylation of viruses suggests the role of shared carbohydrate epitopes, no correlation was observed between hemagglutinin-inhibition titers and the induction of antiganglioside antibodies after influenza vaccination.

Background  Influenza surveillance is important to identify circulating, emerging/reemerging strains and unusual epidemiological trends. With these objectives, a multisite human influenza surveillance network was initiated in India in 2004.

Methods  Epidemiologic data and throat swabs for laboratory testing were collected from patients with influenza-like illness (ILI) and severe acute respiratory infections (SARI). Virus isolation was carried out in Madin–Darby canine kidney cells and strains identified by hemagglutination inhibition assay. Meteorological data were collected.

Results  From September 2004 to December 2008, 617 (4·43%) of 13928 cases yielded isolates: 27·8% were influenza A(H1N1), 29·8% were type A(H3N2), and 42·3% were type B. The yearly type and subtype distribution varied significantly from site to site. Peak influenza activity was observed from June to August in Delhi, Pune, and Kolkata and October to December in Chennai. Maximum influenza activity was seen during the rains in Delhi, Pune, Chennai, and Kolkata in correlation with virus isolations. Multivariate analysis of ILI cases showed chill/rigors, cough, fatigue, and ILI in family, correlated positively with isolation. Genetic analysis of Indian isolates revealed that viruses matched with vaccine strains by and large. Overlapping between circulating and vaccine component strains of consecutive years was also observed.

Conclusions  Seasonal influenza A(H1N1), H3N2, and type B co-circulated in all regions without any particular pattern of movement of any subtype. Year-round limited influenza activity with peaks during rains was observed. Genetic drifts and varying seasonality in different parts of the country suggest that a staggered timing of vaccination may be appropriate for India.

Background  Viral detection from different respiratory sample types in children with cystic fibrosis (CF) is facilitated by available molecular methods, but optimum sampling strategies have not been identified. In addition, associations between viral detection and respiratory symptoms are not well described.

Objectives  Study goals were to compare molecular detection of viruses from concurrent upper airway and sputum samples in children with CF and to describe relative frequency of respiratory viral infections and identify potential clinical associations.

Methods  We conducted a 2-year prospective surveillance study in 44 children with CF aged 6–18 years. Upper airway and sputum samples were collected quarterly and during pulmonary exacerbations and tested for respiratory syncytial virus (RSV), influenza viruses, parainfluenza viruses types 1–4, human metapneumovirus, coronaviruses, rhinoviruses, and adenoviruses. Physical exams and symptom surveys were used to identify respiratory signs and symptoms.

Results  Upper airway samples were collected at 359 visits; concordance of PCR-based viral detection was examined in a subset of paired upper airway and sputum samples from 21 participants at 92 visits. Rhinovirus was the most commonly detected virus (23·1% overall), and rhinovirus detection was the same for both sample types (21·7% each). Sensitivity and specificity for the detection of rhinovirus in sputum relative to upper airway sampling were 70% and 91·7%, respectively. Respiratory symptoms associated with rhinovirus detection included increased cough, increased nasal congestion, increased sputum production, and wheezing.

Conclusions  A relatively high frequency of rhinovirus detection was observed by either upper airway or sputum samples, and clinical findings suggest a significant-associated symptom burden.

Objective  Parallel testing of inactivated (split and whole virion) and live vaccine was conducted to compare the immunogenicity and protective efficacy against homologous and heterosubtypic challenge by H5N1 highly pathogenic avian influenza virus.

Method  Four experimental live vaccines based on two H5N1 influenza virus strains were tested; two of them had hemagglutinin (HA) of A/Vietnam/1203/04 strain lacking the polybasic HA cleavage site, and two others had hemagglutinins from attenuated H5N1 virus A/Chicken/Kurgan/3/05, with amino acid substitutions of Asp54/Asn and Lys222/Thr in HA1 and Val48/Ile and Lys131/Thr in HA2 while maintaining the polybasic HA cleavage site. The neuraminidase and non-glycoprotein genes of the experimental live vaccines were from H2N2 cold-adapted master strain A/Leningrad/134/17/57 (VN-Len and Ku-Len) or from the apathogenic H6N2 virus A/Gull/Moscow/3100/2006 (VN-Gull and Ku-Gull). Inactivated H5N1 and H1N1 and live H1N1 vaccine were used for comparison. All vaccines were applied in a single dose. Safety, immunogenicity, and protectivity against the challenge with HPAI H5N1 virus A/Chicken/Kurgan/3/05 were estimated.

Results  All experimental live H5 vaccines tested were apathogenic as determined by weight loss and conferred more than 90% protection against lethal challenge with A/Chicken/Kurgan/3/05 infection. Inactivated H1N1 vaccine in mice offered no protection against challenge with H5N1 virus, while live cold-adapted H1N1 vaccine reduced the mortality near to zero level.

Conclusions  The high yield, safety, and protectivity of VN-Len and Ku-Len made them promising strains for the production of inactivated and live vaccines against H5N1 viruses.

Please cite this paper as: Peltola et al. (2011) Pandemic influenza A (H1N1) virus in households with young children. Influenza and Other Respiratory Viruses DOI: 10.1111/j.1750-2659.2011.00289.x.

Elevation of liver transaminase levels is a frequent observation during systemic infections. The aim of our study was to investigate liver damage during pandemic 2009 influenza A/H1N1 infection in comparison with seasonal influenza. Serum levels of aspartate aminotransferase, alanine aminotransferase, and gamma-glutamyl transpeptidase (GGT) were significantly higher in patients with pandemic influenza compared to seasonal influenza, which was strongly correlated with hypoxia. Moreover, a positive correlation between C-reactive protein and serum GGT, alkaline phosphatase, and lactate dehydrogenase was noticed. Our findings support the hypothesis that the pandemic 2009 influenza A/H1N1 is an illness with a significant immune response to infection leading to hepatocellular injury.

Background  Limitations of the current annual influenza vaccine have led to ongoing efforts to develop a ‘universal’ influenza vaccine, i.e., one that targets a ubiquitous portion of the influenza virus so that the coverage of a single vaccination can persist for multiple years.

Objectives  To estimate the economic value of a ‘universal’ influenza vaccine compared to the standard annual influenza vaccine, starting vaccination in the pediatric population (2–18 year olds), over the course of their lifetime.

Patient/Methods  Monte Carlo decision analytic computer simulation model.

Results  Universal vaccine dominates (i.e., less costly and more effective) the annual vaccine when the universal vaccine cost ≤$100/dose and efficacy ≥75% for both the 5- and 10-year duration. The universal vaccine is also dominant when efficacy is ≥50% and protects for 10 years. A $200 universal vaccine was only cost-effective when ≥75% efficacious for a 5-year duration when annual compliance was 25% and for a 10-year duration for all annual compliance rates. A universal vaccine is not cost-effective when it cost $200 and when its efficacy is ≤50%. The cost-effectiveness of the universal vaccine increases with the duration of protection.

Conclusions  Although development of a universal vaccine requires surmounting scientific hurdles, our results delineate the circumstances under which such a vaccine would be a cost-effective alternative to the annual influenza vaccine.

Background  Standardization of inactivated influenza vaccines by hemagglutinin (HA) content is performed by the single radial immunodiffusion (SRID) method. Regulatory agencies prepare, calibrate, and distribute SRID reagent standards necessary for testing of seasonal influenza vaccines, and a similar process is used to produce potency reagents for candidate pandemic influenza vaccines that are manufactured for emergency stockpiles.

Objectives  Because of the concerns in generating a timely strain-specific potency antiserum for an emerging pandemic virus, we evaluated the feasibility of using heterologous potency reference antiserum as a replacement for a strain-specific (homologous) antiserum in the SRID potency assay for stockpiled H5N1 vaccines.

Results  The results indicate that a heterologous H5N1 antiserum can be used to determine the accurate potency of inactivated H5N1 influenza vaccines. Additionally, when H5N1 vaccine was subjected to an accelerated stability protocol, both homologous and heterologous antisera provided similar measurements of vaccine potency decline. Limitations to the heterologous antiserum approach to potency determination were shown by the inability of antiserum to recent seasonal H1N1 viruses to work in an SRID assay with the 2009 pandemic H1N1 A/California/07/2009 antigen.

Conclusions  The data demonstrate the feasibility of using heterologous antiserum for potency determination of at least some candidate vaccines in case of a shortage or delay of homologous antiserum. Further, the results suggest the prudence of stockpiling a broad library of potency reagents including many strains of influenza viruses with pandemic potential to provide an added measure of assurance that reagent production would not be a bottleneck to vaccine production during a pandemic.

Background  Following the outbreaks of 2009 pandemic H1N1 infection, rapid influenza diagnostic tests have been used to detect H1N1 infection. However, no meta-analysis has been undertaken to assess the diagnostic accuracy when this manuscript was drafted.

Methods  The literature was systematically searched to identify studies that reported the performance of rapid tests. Random effects meta-analyses were conducted to summarize the overall performance.

Results  Seventeen studies were selected with 1879 cases and 3477 non-cases. The overall sensitivity and specificity estimates of the rapid tests were 0·51 (95%CI: 0·41, 0·60) and 0·98 (95%CI: 0·94, 0·99). Studies reported heterogeneous sensitivity estimates, ranging from 0·11 to 0·88. If the prevalence was 30%, the overall positive and negative predictive values were 0·94 (95%CI: 0·85, 0·98) and 0·82 (95%CI: 0·79, 0·85). The overall specificities from different manufacturers were comparable, while there were some differences for the overall sensitivity estimates. BinaxNOW had a lower overall sensitivity of 0·39 (95%CI: 0·24, 0·57) compared with all the others (P-value <0·001), whereas QuickVue had a higher overall sensitivity of 0·57 (95%CI: 0·50, 0·63) compared with all the others (P-value = 0·005).

Conclusions  Rapid tests have high specificity but low sensitivity and thus limited usefulness.

This work aimed at studying the link between some climatic factors and the occurrence of influenza in Niamey, Niger. Patients with influenza like illness or severe acute respiratory illness were recruited through a sentinel network. A nasopharyngeal swab was sampled and tested for influenza viruses A and B by RT-PCR. Time series of daily counts of influenza cases and climatic factors were linked using a generalized additive model. Among the 320 patients recruited, 76 were confirmed positive for influenza. Influenza cases increased significantly with minimal temperatures and high visibility. This work brings some valuable explanation to the impact of low temperatures on influenza transmission.

Background  Development of influenza vaccines that induce mucosal immunity has been highlighted by the World Health Organisation as a priority (Vaccine 2005;23:1529). Dose-sparing strategies and an efficient mass-vaccination regime will be paramount to reduce the morbidity and mortality of a future H5N1 pandemic.

Objectives  This study has investigated the immune response and the dose-sparing potential of a chitosan-adjuvanted intranasal H5N1 (RG-14) subunit (SU) vaccine in a mouse model.

Methods  Groups of mice were intranasally immunised once or twice with a chitosan (5 mg/ml)-adjuvanted SU vaccine [7·5, 15 or 30 μg haemagglutinin (HA)] or with a non-adjuvanted SU vaccine (30 μg HA). For comparison, another group of mice were intranasally immunised with a whole H5N1 (RG-14) virus (WV) vaccine (15 μg HA), and the control group consisted of unimmunised mice.

Results  The chitosan-adjuvanted SU vaccine induced an immune response superior to that of the non-adjuvanted SU vaccine. Compared with the non-adjuvanted SU group, the chitosan-adjuvanted SU vaccine elicited higher numbers of influenza-specific antibody-secreting cells (ASCs), higher concentrations of local and systemic antibodies and correspondingly an improved haemagglutination inhibition (HI) and single radial haemolysis (SRH) response against both the homologous vaccine strain and drifted H5 strains. We measured a mixed T-helper 1/T-helper 2 cytokine response in the chitosan-adjuvanted SU groups, and these groups had an increased percentage of virus-specific CD4⁺ T cells producing two Thelper 1 (Th1) cytokines simultaneously compared with the non-adjuvanted SU group. Overall, the WV vaccine induced higher antibody concentrations in sera and an HI and SRH response similar to that of the chitosan-adjuvanted SU vaccine. Furthermore, the WV vaccine formulation showed a stronger bias towards a T-helper 1 profile than the SU vaccine and elicited the highest frequencies of CD4⁺ Th1 cells simultaneously secreting three different cytokines (INFγ⁺, IL2⁺ and INFα⁺). As expected, two immunisations gave a better immune response than one in all groups. The control group had very low or not detectable results in the performed immunoassays.

Conclusion  The cross-clade serum reactivity, improved B- and T-cell responses and dose-sparing potential of chitosan show that a chitosan-adjuvanted intranasal influenza vaccine is a promising candidate vaccine for further preclinical development.

Background  Vaccination is considered the most effective means of reducing influenza burden. The emergence of H5N1 and pandemic spread of novel H1N1/2009 viruses reinforces the need to have strategies in place to rapidly develop seed viruses for vaccine manufacture.

Methods  Candidate pandemic vaccine strains consisting of the circulating strain haemagglutinin (HA) and neuraminidase (NA) in an A/PR/8/34 backbone were generated using alternative synthetic DNA approaches, including site-directed mutagenesis of DNA encoding related virus strains, and rapid generation of virus using synthetic DNA cloned into plasmid vectors.

Results  Firstly, synthetic A/Bar Headed Goose/Qinghai/1A/2005 (H5N1) virus was generated from an A/Vietnam/1194/2004 template using site-directed mutagenesis. Secondly, A/Whooper Swan/Mongolia/244/2005 (H5N1) and A/California/04/09 (H1N1) viruses were generated using synthetic DNA encoding the viral HA and NA genes. Replication and antigenicity of the synthetic viruses were comparable to that of the corresponding non-synthetic viruses.

Conclusions  In the event of an influenza pandemic, the use of these approaches may significantly reduce the time required to generate and distribute the vaccine seed virus and vaccine manufacture. These approaches also offer the advantage of not needing to handle wild-type virus, potentially diminishing biocontainment requirements.

Background/objective  We evaluated the sensitivity of PCR on oral fluids in detecting influenza virus in vaccinated and non-vaccinated pigs.

Methods  Three-week-old influenza-free pigs were divided into three groups: (i) control, non-vaccinated, (ii) vaccinated with a commercial, heterologous vaccine, and (iii) vaccinated with an experimental, homologous vaccine. After vaccination, an influenza-infected pig was placed in contact with each of the groups. Individual nasal swabs and pen oral fluids were collected daily. Viral RNA was tested for the presence of influenza by RRT-PCR and virus isolation attempted from oral fluids. A pen was considered positive if at least one nasal swab was positive.

Results  Based on nasal swab results, 43·8% of pens were detected positive but only 35% based on oral fluids. Overall sensitivity of oral fluids was 80%, and virus was isolated from 51% of RRT-PCR-positive oral fluids. The kappa coefficient for agreement (ĸ) between oral fluids and nasal swabs was 0·82. Among groups, ĸ was 1 (95% CI, 1–1), 0·74 (95% CI, 0·55–0·92), and 0·76 (95% CI, 0·5–1) for control, heterologous, and homologous-vaccinated groups, respectively. There was less agreement when within pen prevalence was 10% or less. Probability of detecting influenza virus in oral fluids was 99% when within pen prevalence was higher than 18% and decreased to 69% when prevalence was 9%.

Conclusions  Results indicated that pen-based collection of oral fluids is a sensitive method to detect influenza even when within pen prevalence is low and when pigs have been vaccinated and highlight the potential use of oral fluids for influenza surveillance.

Purpose  The main purpose of vaccination is to generate immunological memory providing enhanced immune responses against infectious pathogens. The standard and most commonly used assay for influenza vaccine immunogenicity evaluation is a hemagglutination inhibition assay (HAI). It is clear now that HAI assay is unable to properly assess the proven protective immunity elicited by live attenuated influenza vaccines (LAIV). New methods need to be developed for more accurate LAIV immunogenicity assessment and prediction of vaccine efficacy among target populations.

Objective  Randomized placebo-controlled study of memory B- and T-cell responses to intranasal LAIV in young adults.

Methods  A total of 56 healthy young adults 18–20 years old received seasonal monovalent LAIV. Mucosal memory B-cell responses were measured by IgA avidity assessment in nasal swabs. CD4 memory T cells in peripheral blood were examined by the expression of CD45RO marker and in functional test by the ability of virus-specific T cells to maintain the trogocytosis with antigen-loaded target cells.

Results  Intranasal LAIV immunization enhances mucosal IgA avidity even without reliable increases in antibody titers. At the day 21 after vaccination, up to 40% of subjects demonstrated significant increases in both total and virus-specific CD4 memory T cells that were observed regardless of seroconversion rate measured by HAI assay.

Conclusion  The data suggest that immunogenicity of LAIV vaccines should be evaluated on the mucosal and cellular immunity basis. The assays applied could be used to support influenza clinical trials through preliminary screening of volunteers and subsequent measurement of anti-influenza in immunity.

Background  Prior to detection of an antibody response toward influenza viruses using the hemagglutination inhibition assay (HAI), sera are routinely treated to inactivate innate inhibitors using both heat inactivation (56°C) and recombinant neuraminidase [receptor-destroying enzyme (RDE)].

Objectives  We revisited the contributions of innate serum inhibitors toward interference with influenza viruses in immune assays, using murine sera, with emphasis on the interactions with influenza A viruses of the H3N2 subtype.

Methods  We used individual serum treatments: 56°C alone, RDE alone, or RDE + 56°C, to treat sera prior to evaluation within HAI, microneutralization, and macrophage uptake assays.

Results  Our data demonstrate that inhibitors present within untreated murine sera interfere with the HAI assay in a manner that is different from that seen for the microneutralization assay. Specifically, the γ class inhibitor α₂-Macroglobulin (A2-M) can inhibit H3N2 viruses within the HAI assay, but not in the microneutralization assay. Based on these findings, we used a macrophage uptake assay to demonstrate that these inhibitors can increase uptake by macrophages when the influenza viruses express an HA from a 1968 H3N2 virus isolate, but not a 1997 H3N2 isolate.

Conclusions  The practice of treating sera to inactivate innate inhibitors of influenza viruses prior to evaluation within immune assays has allowed us to effectively detect influenza virus-specific antibodies for decades. However, this practice has yielded an under-appreciation for the contribution of innate serum inhibitors toward host immune responses against these viruses, including contributions toward neutralization and macrophage uptake.

Background  Sarcoidosis is an inflammatory, granulomatous disorder of unknown etiology. The role of cellular and humoral immune systems in this disease is unclear, whereas dysregulation of the immune system is suggested. Patients with sarcoidosis show diverse responses while exposed to various antigens. Although influenza vaccination is recommended in pulmonary sarcoidosis, its efficacy and safety has not been investigated.

Objectives  To evaluate safety and immunogenicity of influenza vaccine in patients with sarcoidosis.

Patients/Methods  Influenza vaccination was performed in 23 eligible patients with sarcoidosis (SP) and 26 healthy controls (HC). Antibody titers against H1N1, H3N2, and B influenza virus antigens were evaluated just before and 1 month after vaccination. Patients were followed for 6 months to assess vaccine safety.

Results  Serological response and magnitude of changes in antibody titers against influenza vaccine antigens were comparable between SPs and HCs. Women showed a better serological response against B antigen (P = 0·034) than men. Twenty-four-hour urine calcium was associated with antibody response against H1N1 [correlation coefficient (CC) = 0·477, P = 0·003] and H3N2 (CC = 0·352, P = 0·028) antigens. Serum angiotensin-converting enzyme correlated negatively with antibody response against B antigen (CC = −0·331, P = 0·040). Higher residual volume was associated with fewer rises in antibody titer against H3N2 antigen (CC = −0·377, P = 0·035). No major adverse events or disease flare-up was observed during follow-up.

Conclusions  In this study, influenza vaccination did not cause any major adverse event in SPs, and their serological response was equal to HCs. Studies with larger sample size and a broader selection of subjects could help validate the results of this study.