Influenza‐like illness in healthcare personnel at a paediatric referral hospital: Clinical picture and impact of the disease

Introduction Healthcare personnel (HP) are frequently exposed to influenza and can be a source of transmission to patients and other workers, resulting in high‐cost outbreaks for healthcare institutions. Objectives To analyse the presentation of HP with influenza‐like illness (ILI) and the differences between individuals with influenza confirmed by polymerase chain reaction (PCR) and those with a negative test. The secondary objective was to evaluate the duration of symptomatology and work absenteeism as well as the vaccination rate of HP at a paediatric referral hospital. Methods A cross‐sectional, descriptive study was conducted at a paediatric referral hospital. Clinical and epidemiological data on HP with ILI were collected between January and April 2016. Nasopharyngeal swab for influenza PCR was obtained from one in every three workers with ILI. Telephone follow‐up was conducted to document duration of symptoms, complications and absenteeism. Results A total of 164 ILI episodes were evaluated in 162 HP. A swab was obtained in 59 cases, and influenza was detected in 30 cases. The clinical picture of HP with confirmed influenza was similar to that of HP with a negative PCR. Arthralgia was more common in those with influenza (90% vs 58%), with a tendency towards statistical significance. No HP required hospitalization, and 78.5% were absent from work at least 1 day. Conclusions Influenza causes significant morbidity and absenteeism among HP. Influenza infection was confirmed in only half of HP with an ILI on whom a PCR was performed, suggesting that other respiratory viruses can cause a similar pattern.


Introduction:
Healthcare personnel (HP) are frequently exposed to influenza and can be a source of transmission to patients and other workers, resulting in high-cost outbreaks for healthcare institutions.
Objectives: To analyse the presentation of HP with influenza-like illness (ILI) and the differences between individuals with influenza confirmed by polymerase chain reaction (PCR) and those with a negative test. The secondary objective was to evaluate the duration of symptomatology and work absenteeism as well as the vaccination rate of HP at a paediatric referral hospital.

Methods:
A cross-sectional, descriptive study was conducted at a paediatric referral hospital. Clinical and epidemiological data on HP with ILI were collected between January and April 2016. Nasopharyngeal swab for influenza PCR was obtained from one in every three workers with ILI. Telephone follow-up was conducted to document duration of symptoms, complications and absenteeism.
Results: A total of 164 ILI episodes were evaluated in 162 HP. A swab was obtained in 59 cases, and influenza was detected in 30 cases. The clinical picture of HP with confirmed influenza was similar to that of HP with a negative PCR. Arthralgia was more common in those with influenza (90% vs 58%), with a tendency towards statistical significance. No HP required hospitalization, and 78.5% were absent from work at least 1 day.

Conclusions: Influenza causes significant morbidity and absenteeism among HP.
Influenza infection was confirmed in only half of HP with an ILI on whom a PCR was performed, suggesting that other respiratory viruses can cause a similar pattern.

K E Y W O R D S
healthcare personnel, influenza, morbidity

| INTRODUC TI ON
Due to its unique antigenic characteristics, influenza virus infection occurs in annual outbreaks of varying magnitude and severity, leading to substantial morbidity and mortality, which disproportionately affects individuals with immunodeficiency, chronic diseases or those at the extremes of life. However, even people without identifiable risk factors can suffer complications and die from this illness.
Healthcare personnel (HP) are a vulnerable group due to frequent and close exposure to patients infected with influenza virus.
In addition to the risks to one's own health, the infected worker can spread the virus to other patients, workers and their contacts in the community. 1 Such transmission may result in outbreaks involving high costs for healthcare institutions. 2 Annual vaccination of healthcare personnel is one of the main strategies for the prevention of transmission in this population, and a relationship has been documented between the vaccination coverage of healthcare personnel and a decrease in cases of nosocomial influenza, 3  The objective of this study was to analyse the presentation and evolution of HP with influenza-like illness (ILI) in this setting as well as the clinical differences between those with influenza confirmed by polymerase chain reaction (PCR) of a nasopharyngeal swab and those who had a negative test.
The secondary objective was to evaluate the duration of the symptoms and work absenteeism caused by ILI as well as the vaccination rate of the HP at the HIMFG.

| ME THODOLOGY
This study is a cross-sectional, descriptive study performed at the HIMFG, a national referral paediatric teaching hospital. HP who presented with ILI for diagnosis and treatment to the Department of Hospital Epidemiology were included in the study. Clinical and epidemiological information was collected from HP with ILI who were examined at the Department of Hospital Epidemiology between 27 January and 30 April 2016. ILI was defined as any acute-onset episode, including at least one systemic symptom (fever ≥ 38°C, headache or myalgia) as well as a respiratory symptom (cough, odynophagia or respiratory distress). 5 Nasopharyngeal swab for the detection of influenza virus was obtained from one in every three HP with ILI, plus a few other workers according to hospital needs.
Thirty-five swab samples were processed by real-time RT-PCR (Applied Biosystems, Thermo Fisher Scientific corporation, USA) for the influenza A, AH1N1pdm and influenza B viruses, and 19 swabs were processed through the automated extraction of nucleic acids (MagNA Pure ® Compact, Roche) with detection of influenza A and B using an RT-PCR system with microarray visualization (CLART ® PneumoVir, Genomica, Spain). Both techniques employed have a comparable diagnostic accuracy, with a specificity above 95%. 6,7 The HP were followed up by telephone using a previously designed survey to document the duration of the symptoms, the frequency of complications, work absenteeism and transmission to other people at home.

| Statistical analysis
The results are expressed as measures of central tendency and dispersion; simple and cumulative frequencies were calculated. The group in which a nasopharyngeal swab was obtained was divided into subjects with confirmed influenza infection and subjects with a negative influenza test. Clinical and epidemiological characteristics were compared using Student's t test or the Mann-Whitney U test for continuous variables and the chi-squared test or Fisher's exact test for categorical variables. Statistical analyses were performed using SPSS ® software version 20.

| RE SULTS
One hundred and sixty-two HP, who reported a total of 164 episodes of ILI, were examined ( Figure 1). A nasopharyngeal swab was used to detect influenza virus in 59 (36%) of the 164 episodes. Table 1 shows the clinical and demographic characteristics of the subjects enrolled in the study. Almost three-quarters of the staff who were examined for ILI were women, which represents a greater proportion than that found in the total population of hospital workers (74% vs 63.5%, P = .004).
Influenza virus was detected in 30 of the 59 nasopharyngeal swab specimens (50.8%), with the following distribution of subtypes: 16 influenza AH3N2, seven influenza AH1N1, six influenza B and one unidentified subtype of influenza A ( Figure 2). Oseltamivir was given in 125 of the 164 episodes (76%), depending on the evolution time of the symptoms at the time of evaluation.
The frequencies of cardinal symptoms, including fever, headache, cough, myalgia and arthralgia, were compared in the subgroup in which nasopharyngeal swabs were obtained, and no differences were found between the groups with and without influenza ( Table 2).
Telephone follow-up was performed for 79 of the 162 HP (49%) to assess the morbidity of the disease. None of the patients for which a follow-up was performed had a fatal outcome or required hospitalization. Four patients (5.05%) required treatment with nebulizations, and ten patients (12.6%) reported secondary cases of influenza at home.
For 62 cases (78.5%), no statistically significant difference in the duration of symptoms was found between patients with confirmed influenza and those with a negative viral panel (P > .05; Table 3).

| D ISCUSS I ON
Influenza is one of the most significant infections in HP due to its frequency in the winter season, the morbidity and absenteeism that it entails and the risk of transmission to patients susceptible to severe illness or even death.
The 2015-2016 season was characterized by low influenza activity from October to December. However, beginning in the final week of January, a notable increase in cases of respiratory and influenza illness occurred both in patients and HP at the HIMFG, which is consistent with reports by the General Direction of Epidemiology (Dirección General de Epidemiología) at the national level. 8 A high proportion of HP who sought ILI care were women, which is consistent with reports in the literature because women with ILI have been shown to be more likely to seek medical care than men. 9 As shown in Table 1, there was a greater proportion of fever and chills among HP who were swabbed. As PCR was usually obtained from the first HP who consulted with ILI every day, a possible explanation for this finding is that HP with fever and chills were more likely to consult earlier in the day compared to workers without fever.
The most frequent symptoms in HP with influenza were fever, chills and headache, which were present in more than 90% of cases, followed by myalgia, arthralgia and cough, with a frequency greater than 80%. In contrast, in a study of HP in Chicago in 2014, only 51% of the participants presented with fever as a symptom. 10  Although in our population the proportions of vaccinated individuals were similar among workers with confirmed influenza and those with a negative test, the study was not designed to evaluate vaccine efficacy, and the sample size was not sufficient to obtain conclusions about this aspect.
Likewise, multifaceted strategies that include hospital policies for mandatory vaccination have been shown to be effective for increasing staff adherence to influenza vaccination. 4 The limitations of the study include the fact that the detection of HP with ILI was passive and did not cover the entire influenza season, as it began in January. However, HP were constantly