Knowledge, Attitudes, and Practices of US Travelers to Asia Regarding Seasonal Influenza and H5N1 Avian Influenza Prevention Measures
The data were presented orally at the CISTM Budapest, May 2009.
Emad Yanni, MD, Division of Global Migration and Quarantine, National Center for Emerging and Zoonotic Infectious Diseases, Centers for Disease Control and Prevention, 1600 Clifton Road, MS-E03, Atlanta, GA 30333, USA. E-mail: Eyanni@cdc.gov
Background. International travel is a potential risk factor for the spread of influenza. In the United States, approximately 5%–20% of the population develops an influenza-like illness annually. The purpose of this study was to describe the knowledge, attitude, and practices of US travelers to Asia regarding seasonal influenza and H5N1 avian influenza (AI) prevention measures.
Methods. We surveyed travelers to Asia waiting at the departure lounges of 38 selected flights at four international airports in New York, Chicago, Los Angeles, and San Francisco. Of the 1,301 travelers who completed the pre-travel survey, 337 also completed a post-travel survey. Univariate and multivariate logistic regression were used to calculate prevalence odds ratios (with 95% CI) to compare foreign-born (FB) to US-born travelers for various levels of knowledge and behaviors.
Results. Although the majority of participants were aware of influenza prevention measures, only 41% reported receiving the influenza vaccine during the previous season. Forty-three percent of participants reported seeking at least one type of pre-travel health advice, which was significantly higher among US-born, Caucasians, traveling for purposes other than visiting friends and relatives, travelers who received the influenza vaccine during the previous season, and those traveling with a companion. Our study also showed that Asians, FB travelers, and those working in occupations other than health care/animal care were less likely to recognize H5N1 AI transmission risk factors.
Conclusion. The basic public health messages for preventing influenza appear to be well understood, but the uptake of influenza vaccine was low. Clinicians should ensure that all patients receive influenza vaccine prior to travel. Tailored communication messages should be developed to motivate Asians, FB travelers, those visiting friends and relatives, and those traveling alone to seek pre-travel health advice as well as to orient them with H5N1 AI risk factors.
International travel, human behavior, and changing demographics are major risk factors for the emergence of infectious diseases.1 Each year in the United States, over 60 million people travel abroad for tourism, business, or other reasons.2 Of these, 12 million people travel to Asia, which is increasing in popularity as a tourism and business travel destination. In addition, because of the changing demographics of the US population, an increasing percentage of US residents were born in or have relatives living in Asia.3
Influenza is one of the most common infectious diseases which cause severe illness in millions of people every year.4 Travel and transportation are associated with outbreaks of seasonal and, most recently, with a pandemic strain of novel H1N1 influenza, which spread worldwide in 6 weeks.5 Before the 2009 pandemic H1N1 influenza virus emerged, public health professionals expected that the next pandemic influenza would be a variant of the H5N1 avian influenza virus (H5N1 AI) that emerged in Hong Kong in 1997.6 Because influenza viruses can easily reassort, scientists remain concerned that a virus that is as transmissible as H1N1 will reassort with a virus that is as lethal as H5N1 AI.
In 2008, because of the concern about H5N1 AI, we conducted a study among US travelers to Asia to assess their knowledge, attitudes, and practices (KAP) regarding seasonal influenza and H5N1 AI prevention measures, and to assess their practices during travel that may pose a risk for exposure to novel influenza strains. Understanding KAP regarding influenza is necessary to prepare travelers for future pandemics and for the management of seasonal influenza as well.
The survey was conducted from June through September 2008 among travelers to Asia at the departure lounges of four international airports in the United States; pre- and post-travel questionnaires were designed to compare travelers' knowledge of influenza prevention measures to their behavior during travel and assess how they would manage their illness if they became ill. The pre-travel component included questions about demographics, itinerary, purpose of travel, planned activities, influenza vaccination status, potential barriers to vaccination, and knowledge about influenza modes of transmission, as well as preventive measures to be taken during travel. The post-travel component included questions about destination, duration of travel, trip activities, illness during travel, symptoms, and risk factors for avian influenza transmission. The post-travel survey was conducted among those who participated in the pre-travel survey and completed the post-travel survey after returning from Asia.
Sample Size Estimate
Since persons who received influenza vaccine are likely to be aware of other influenza prevention measures, we used the US 2007 seasonal influenza vaccination survey data, which indicated that 40% of respondents had received the influenza vaccine (CDC Internal Report: Seasonal Influenza Survey—American Institute for Research, May 2007), as a proxy to estimate the study sample size. A sample of 1,024 travelers to Asia was chosen to achieve sufficient power to estimate the KAP of travelers regarding influenza prevention measures, with a precision of 40% ± 3% and 95% level of confidence.
Based on Department of Commerce estimates of airports with the most US travelers to Asia,2 we targeted John F. Kennedy International Airport (JFK), O’Hare International Airport (ORD), Los Angeles International Airport (LAX), and San Francisco International Airport (SFO). The survey data were collected among a convenience sample of the travelers waiting at the boarding areas of 38 flights during the 2 hours prior to their departure. Asian countries with direct, nonstop commercial flights from the United States included China (n = 8), Hong Kong (n = 4), Japan (n = 10), India (n = 7), South Korea (n = 4), Thailand (n = 3), and Singapore (n = 2). Eligible survey participants were ≥18 years of age, had lived in the United States for >6 months, and could read English. Only one survey was collected per traveling family. Passengers waiting at the first-class lounge/club or those who arrived shortly before boarding were therefore not included in the survey.
Data Handling and Analysis
Data were entered into a database and analyzed using SAS software version 9.1. Univariate and multivariate logistic regressions were used to calculate prevalence odds ratios (OR) with 95% confidence intervals (CI). We compared foreign-born (FB) travelers with US-born travelers because previous studies have shown that immigrant adults and their children are less likely to be current on routine immunizations than their US-born counterparts.7,8 The case definition used for travel-associated influenza-like illness (ILI) was fever with cough or sore throat during the trip or within 1 week after return. Because of small numbers, we used exact logistic regression to analyze ILI in the post-travel survey. The survey protocol and questionnaires were reviewed and exempted as research by the institutional review board at the Centers for Disease Control and Prevention.
We approached 3,935 travelers to Asia, of whom 2,046 (52%) were ineligible (visitors to the United States returning home, short-term US residents for less than 6 months, or people with language barriers). Of 1,889 eligible travelers, 1,301 (69%) completed the pre-travel questionnaire. Of these, 600 provided their contact information and agreed to complete the post-travel survey after returning from Asia, and 337 (56%) completed the post-travel survey either by mail, telephone, or online. Participants in the pre- and post-travel surveys differed significantly by age, race, occupation, and country of birth (Table 1).
Table 1. Sociodemographic characteristics of US travelers to Asia
| 18–34||38.0 (35.3–40.7)||28.9 (23.9–33.8)||0.013|
| 35–54||43.1 (40.4–45.9)||46.9 (41.4–52.3)|| |
| 55–64||12.9 (11.0–14.7)||17.4 (13.3–21.5)|| |
| 65+||6.0 (4.7–7.4)||6.8 (4.1–9.6)|| |
| White||41.5 (38.8–44.2)||53.9 (48.5–59.2)||<0.0001|
| Asian||50.9 (48.2–53.7)||37.6 (32.4–42.7)|| |
| Other races||7.6 (6.1–9.0)||8.6 (5.6–11.6)|| |
| Male||52.0 (49.3–54.8)||52.7 (42.0–52.7)|| |
| Female||48.0 (45.3–50.7)||47.3 (47.3–58.1)||0.125|
|Country of birth|
| United States||50.0 (47.2–52.8)||65.0 (59.7–70.2)|| |
| Other||50.0 (47.2–52.8)||35.0 (29.8–40.3)||<0.0001|
| China||9.9||5.0|| |
| India||9.7||6.3|| |
| Japan||5.2||4.1|| |
| Korea||5.1||1.9|| |
| Philippines||3.3||1.9|| |
| Hong Kong||2.8||2.8|| |
| Taiwan||2.1||1.9|| |
| Vietnam||1.9||2.8|| |
| Thailand||1.5||0.6|| |
| Others||8.5||7.7|| |
| Married||60.2 (57.5–62.8)||62.5 (57.3–67.7)|| |
| Single||39.8 (37.2–42.5)||37.5 (32.3–42.7)||0.443|
|Highest level of education|
| High school||18.9 (16.8–21.0)||14.1 (10.3–17.8)|| |
| University||41.3 (38.6–44.0)||40.4 (35.2–45.7)||0.061|
| Graduate degree||39.8 (37.1–42.5)||45.5 (40.2–50.9)|| |
| Student||19.9 (17.7–22.1)||12.0 (8.5–16.0)|| |
| Nonstudent||80.1 (78.0–82.3)||88.0 (84.5–91.5)||0.0009|
| Visiting friends and relatives||37.1 (34.5–39.8)||31.9 (27.1–36.9)||0.08|
| Others||62.9 (60.0–65.5)||68.1 (62.8–73.1)|| |
Of the 1,301 participants who answered the pre-travel survey, 494 (42%) planned to visit more than one Asian country during their trip. The top three destination countries were China (including Hong Kong), Japan, and India (Table 2). The main reasons for travel were vacation (40%), visiting friends and relatives (37%), and business (26%) (Table 2). US-born travelers were more likely to travel for work or vacation while FB travelers were more likely to visit their friends and relatives (VFR). FB travelers were also more likely to travel for longer duration than US-born travelers (Table 2). US-born travelers were more likely than FB travelers to plan the following activities: attend large gatherings/events, visit food markets, eat from street food vendors, and travel into rural areas (Table 2).
Table 2. Trip characteristics, and travelers' knowledge of influenza symptoms, and preventive measures (n = 1,301)
| China||545 (42)||239 (40)||274 (46)|
| Japan||263 (20)||110 (18)||140 (23)|
| India†||246 (19)||137 (23)||93 (16)|
| Travel reason*|
| Vacation†||507 (40)||199 (33)||269 (45)|
| VFR†||468 (37)||322 (54)||114 (19)|
| Business†||325 (26)||107 (18)||202 (34)|
| Study/research†||126 (10)||35 (6)||84 (14)|
| Volunteer/missionary†||44 (4)||12 (2)||28 (5)|
| Attending meetings||30 (2)||11 (2)||17 (3)|
| 2008 Olympic games||12 (1)||6 (1)||5 (1)|
| Adoption||5 (0.4)||0 (0)||3 (0.5)|
| Medical treatment||4 (0.3)||3 (0.5)||1 (0.2)|
| Home†||648 (51)||434 (73)||169 (28)|
| Hotel†||609 (48)||177 (30)||329 (55)|
| Hostel†||105 (8)||32 (5)||62 (10)|
| School†||60 (5)||11 (2)||45 (8)|
| Trip duration†|
| <1 wk||85 (7)||27 (5)||55 (9)|
| 1–2 wk||455 (38)||148 (25)||271 (45)|
| 3–4 wk||310 (26)||173 (29)||119 (20)|
| 1–5 mo||279 (23)||169 (28)||92 (15)|
| 6–12 mo||34 (3)||20 (3)||12 (2)|
| >1 yr||45 (4)||23 (4)||17 (3)|
| Planned activities*|
| Attend large event†||317 (25)||104 (17)||185 (31)|
| Visit food markets†||403 (32)||138 (23)||235 (39)|
| Eat from street vendors†||390 (31)||150 (25)||219 (37)|
| Travel to rural areas†||303 (24)||103 (17)||175 (29)|
| Knowledge of symptoms*|
| Fever†||1,111 (89)||481 (80)||553 (92)|
| Sore throat||871 (70)||412 (69)||404 (68)|
| Cough||811 (65)||385 (64)||375 (63)|
| Muscle aches†||859 (69)||330 (55)||476 (80)|
| Fatigue†||711 (57)||253 (42)||413 (69)|
| Knowledge of preventive measures*|
| Hand washing†||1,122 (89)||495 (83)||548 (92)|
| Avoiding people with flu symptoms||1,018 (81)||454 (76)||492 (82)|
| Getting influenza vaccine†||943 (75)||407 (68)||476 (80)|
| Covering mouth while sneezing||846 (67)||385 (64)||400 (67)|
| Avoiding crowded areas||695 (55)||305 (51)||345 (58)|
| Antibiotics||209 (17)||102 (17)||95 (16)|
| Antiviral medicines||172 (14)||70 (12)||90 (15)|
Knowledge of Influenza Symptoms, and Preventive Measures
Both FB and US-born travelers were aware of most influenza symptoms and prevention measures (Table 2), but US-born travelers were more aware that the following symptoms could indicate influenza: nausea (OR = 2.67, CI = 2.08–3.43), vomiting (OR = 2.88, CI = 2.22–3.73), diarrhea (OR = 2.58, CI = 1.92–3.48), and muscle ache (OR = 3.04, CI = 2.29–4.03).
Influenza Vaccine Coverage
Overall, 692 (56%) participants did not receive influenza vaccine during the previous season and 3% did not know whether they had received the vaccine. Reported reasons for not being vaccinated included not thinking they needed the influenza vaccine (57%), fear of becoming ill from the vaccine (13%), fear of needles (7%), belief that the vaccine had no effect (5%), receipt of vaccine >1 year earlier and not thinking they needed it again (4%), and not believing in vaccination (4%) (more than one response option). Of note, cost, access to health insurance, and lack of time before travel were rarely mentioned as barriers for not getting the influenza vaccine.
Forty-one percent of participants received the seasonal influenza vaccine during the previous season. Vaccination rates were as follows: 36% of survey participants aged 18 to 49; 52% of participants aged 50 to 64 years; and 67% of persons aged 65 years and older. Influenza vaccination rates were significantly higher among married participants than single participants (OR = 1.61, CI = 1.20–2.17) and in age groups 50 to 64 (OR = 1.74, CI = 1.27–2.40), and 65+ (OR = 3.80, CI = 2.10–7.13) than in the 18 to 49 year group. Neither the country of birth nor the travel purpose affected the vaccine coverage rate.
Attitudes Toward Seasonal Influenza Risk of Exposure
Sixty-five percent of participants thought they were at risk for influenza during their trip to Asia. US-born travelers, travelers with university-level educational attainment, and travelers for other purposes than visiting friends and relatives (non-VFR) were significantly more likely to consider that risk, compared with FB, high school graduates, and VFR travelers. However, most respondents (75%) were not worried about acquiring seasonal influenza during their trip to Asia.
Fewer than half (43%) of the participants (n = 548) reported seeking pre-travel health/medical advice (Table 3) from at least one source. Among those who sought any form of pre-travel advice, the internet was the most common source of travel health information (53%), followed by primary health care (PHC) provider (50%), travel health specialist (20%), and family/friend (18%) (more than one response option). Of note, US-born travelers were more likely to use the internet and a travel medicine specialist as a source of pre-travel health advice. Seeking any pre-travel advice was significantly more common among US-born, non-VFR, Caucasians, travelers who received the seasonal influenza vaccine during the previous season, and those traveling with a companion (Table 4).
Table 3. Sources of health information among travelers who sought pre-travel advice (n = 548)*
|Internet in general†||292 (53)||229 (69)||63 (37)|
| Health/travel website||183 (33)||133 (40)||50 (30)|
| CDC travelers' health website||109 (20)||96 (29)||13 (7)|
|Primary care practitioner||274 (50)||184 (55)||90 (53)|
|Travel medicine specialist†||107 (20)||92 (28)||15 (9)|
|Friend/relative||97 (18)||59 (18)||38 (22)|
|Travel book||43 (8)||32 (10)||11 (7)|
|Travel agent/trip organizer||40 (7)||27 (8)||13 (8)|
Table 4. Characteristics of US travelers to Asia who sought pre-travel health advice (n = 1,271)
| Female||1.12 (0.89–1.39)||0.34||1.20 (0.91–1.59)||0.20|
| 50–64||1.42 (1.09–1.88)||0.01||0.98 (0.70–1.38)||0.89|
| 65+||1.69 (1.04–2.74)||0.03||1.16 (0.62–2.15)||0.65|
| Single||0.96 (0.76–1.21)||0.71||1.15 (0.85–1.57)||0.36|
| High school or lower*|
| University||1.11 (0.81–1.53)||0.51||1.09 (0.75–1.61)||0.64|
| Graduate or higher||1.34 (0.97–1.85)||0.07||1.34 (0.90–2.00)||0.15|
| White||3.17 (2.49–4.04)||<0.0001||1.64 (1.07–2.53)||0.02|
| Other||2.10 (1.30–3.40)||0.0024||1.47 (0.82–2.65)||0.20|
| US-born||3.10 (2.43–3.96)||<0.0001||1.90 (1.26–2.87)||0.002|
|Trip duration||0.99 (0.99–1.00)||0.75||1.00 (0.99–1.01)||0.26|
| With companions||1.88 (1.48–2.39)||<0.0001||1.73 (1.30–2.31)||0.0002|
| Other||2.77 (2.10–3.50)||<0.0001||1.85 (1.36–2.52)||<0.0001|
| Yes||1.88 (1.49–2.37)||<0.0001||1.80 (1.36–2.38)||<0.0001|
To assess participants' attitudes regarding the risk of exposure to avian influenza, we asked them to agree or disagree with the following statements:
In Asia, people are at risk of getting avian influenza when they are involved in the following activities:
- •Visiting a poultry market: Of 337 respondents, 42% agreed, 24% disagreed, and 34% did not know. Asians (OR = 3.08, CI = 1.68–5.67) and those working in occupations other than health care/animal care (OR = 3.74, CI = 1.21–11.56) were more likely to disagree.
- •Children playing with farm animal and chickens: 53% agreed, 14% disagreed, and 33% did not know. FB travelers were more likely to disagree (OR = 2.50, CI = 1.20–4.90).
- •Participating in slaughtering and cleaning poultry: 54% agreed, 13% disagreed, and 33% did not know. FB travelers (OR = 3.40, CI = 1.60–7.10) and those who did not seek pre-travel advice (OR = 3.20, CI = 1.49–7.39) were more likely to disagree.
Of note, 74% of post-travel survey participants were not concerned about the risk of contact with farm animals and birds and were more likely to be travelers who did not seek pre-travel health advice (OR = 2.72, CI = 1.74–4.26).
To assess the risk behavior of travelers during travel, we asked about their planned activities before their trip and then asked about their actual activities after they had completed their travel. Of 181 travelers who attended large gatherings during their trip, 104 (57%) did not plan that activity before traveling. Of 166 travelers who reported visiting friends and relatives, 68 (41%) did not mention that in their plan of activities, and of 127 who decided to sightsee in rural areas, 72 (57%) did not mention it in their planned activities.
History of Being Ill During or Within a Week After Travel
Of 337 participants in the post-travel survey, 145 (43%) reported having at least one symptom of illness during or within 7 days after travel. In addition, 66 participants (20%) reported visiting their family doctor after returning, either because of illness (n = 16) or for a routine checkup (n = 50). Eleven (3%) participants in the post-travel survey met the ILI case definition, nine of them had not been vaccinated against influenza during the past 12 months. Risk factors for ILI included being non-Asian (OR = 6.95, CI = 1.18–90.98), traveling to India and Nepal (OR = 3.33, CI = 1.39–11.11), and staying for longer durations than 2 weeks (OR = 1.20, CI = 1.06–1.37).
We found gaps between travelers' knowledge, perception of risk, and their behavior in several key areas. There appeared to be a gap between travelers' knowledge of influenza prevention measures and their behavior; although 75% noted the importance of getting seasonal influenza vaccine, only 41% had received a vaccine in the past 12 months. We also found divergence in travelers' perception of vulnerability to influenza: 65% believed they were susceptible to influenza but 75% were not worried about acquiring influenza during travel to Asia. Less-educated, FB, and VFR travelers were less likely to consider the risk.
The influenza vaccine coverage rate in our study (41%) approximated the 2008 to 2009 and 2009 to 2010 US seasonal influenza vaccine coverage rates.9, 10 Despite recommendations, vaccination levels are still suboptimal, especially among the age group 18 to 49 years9–12 who represent most US international travelers.2 The beginning of the 2009 pandemic influenza H1N1 in April 2009 increased public awareness of the potential seriousness of influenza, especially among younger persons. However, the 2009 to 2010 US seasonal influenza vaccine coverage rates indicated large increases for children (16 percentage points higher than in 2008 to 2009), but only a moderate increase for adults without high-risk conditions aged 18 to 49 years (7 percentage points higher than in 2008 to 2009).12 These data underscore the challenges of increasing the coverage in the 18 to 49 year age group.
Reasons given for not getting influenza vaccine indicate the need to counteract common misperceptions about influenza vaccination, such as that the vaccine causes illness or that it has no protective efficacy. The CDC Advisory Committee on Immunization Practices (ACIP) recommends travelers to consider influenza vaccination, preferably at least 2 weeks before departure,10 especially persons at high risk for complications of influenza and who were not vaccinated with influenza vaccine during the preceding fall or winter. Attaining higher coverage rates will require additional influenza vaccination programs in schools, universities, and ethnic medical associations' clinics. In addition, wider use of recall and reminder systems can achieve higher coverage among children and adults recommended for influenza vaccination.10
A large percentage of travelers we surveyed became ill either during or within a week after travel (43%), which was similar to the findings of other studies.13–17 The prevalence of ILI among study participants and their companions was close to the prevalence of diagnosed respiratory infections (7.8%) among returned travelers who visited GeoSentinel network clinics.17 Although the finding was not significant, our study showed that 9 of 11 travelers who developed ILI had not been vaccinated against influenza. A study showed a 25%–34% reduction in ILI prevalence among in-season vaccinated adults.16 Therefore, all travelers should be considered for pre-travel influenza vaccination (both seasonal and H1N1 influenza vaccine) to reduce their risk of infection.10,16
Regarding attitudes toward H5N1 AI, our study found that Asians, FB travelers, those working in occupations other than health care/animal care, and those who did not seek pre-travel advice were less likely to recognize possible risk factors such as contact with farm animals and birds, and participating in slaughtering and cleaning poultry. Although the risk of H5N1 AI to US travelers is still low,18 clinicians should address avian influenza preventive measures, especially among travelers to countries where avian influenza is prevalent in birds and humans.
Many travelers are looking for new experiences and adventures, which can increase their risk of exposure to infectious diseases, including novel influenza strains.13–18 We found that many travelers participated in unplanned activities during their travel, such as visiting rural areas, visiting food markets, and attending large gatherings; thus, clinicians should carefully review travelers' trip itineraries with the expectation that they might change their plans and consider the full range of potential activities and risks in the travel destination.
Our study corroborated the findings of previous studies regarding the health-seeking behavior of travelers, showing that less than half of travelers reported seeking any type of pre-travel health advice,19–22 and approximately 30% were FB travelers. We found that the primary care practitioner was the most common source of pre-travel health advice among FB travelers, followed by the internet and friends or relatives. In addition, several studies, including our own, addressed the underutilization of travel health specialists for pre-travel health advice, compared with primary health care physicians. Travelers who received the influenza vaccine during the previous season were more likely to seek pre-travel health advice which may indicate their awareness of influenza prevention measures. These findings highlight the need to improve outreach to FB and VFR travelers to emphasize the benefits of seeking a quality pre-travel health advice. Many travel health experts are calling for more education of primary care providers in travel medicine topics.19–22 Continuing education in the basics of travel health should be available at provider conferences and at all levels of medical training. Our study also showed that the internet is a key source of health information for travelers, so multi-language and custom-tailored travel-related education messages could be developed and posted at popular websites for travelers.
Strengths and Limitations
The survey findings are subject to the following limitations. First, certain sampling factors [the relatively low response rate on the post-travel survey (56%); difference in age, race, and birth place of participants in pre- and post-travel surveys; restriction of the survey to English-speaking respondents; convenient sampling of travelers waiting to board their flights and the exclusion of passengers waiting at the first-class lounge/club or those who arrived shortly before boarding] may indicate that the results do not represent all US travelers to Asia. Second, self-reported ILI symptoms are not specific for influenza because other etiologic agents can cause influenza-like symptoms. Third, influenza vaccination status and pre-travel health advice-seeking behavior were based on self-report, which might result in under- or overreporting because of recall or social desirability bias. Finally, some of the multiple-choice questions allowed participants to select more than one answer, which limited our ability to perform multivariate logistic regression. The study strengths included surveying a large numbers of travelers to Asia in four major international airports within 3 months which helped improve traveler recall of events and activities.
The basic public health messages for preventing influenza appear to be well understood, but the uptake of influenza vaccine was low, especially among unmarried travelers and younger age groups. Training primary care providers in travel health counseling could prevent travel-related illness, especially among FB travelers who commonly prefer counseling from their primary physicians before traveling. Pre-travel advice should address the likelihood that travelers' planned activities may change during travel, which can increase their risk of exposure to a variety of illnesses, including seasonal or novel strains of influenza. Tailored communication messages regarding influenza prevention measures should be developed to reach high-risk travelers, especially FB travelers and younger travelers who are traveling for longer time periods, through popular internet websites and nontraditional communication channels such as social and ethnic networks that are trusted and commonly used by these groups.
We are indebted to the US Quarantine Station staff in the Chicago, New York, Los Angeles, and San Francisco International Airports and the Travelers' Health Branch staff, for their support in survey implementation: Mary Agocs, Shannon Bachar, Heather Bair-Brake, Andre Berro, Moira Booth, Clive Brown, Kirsten Buckley, Perry Camagong, Tony Chheang, Ellen DeMott, Pauline Han, Kelly Holton, Katherine Johnson, Maggie Koral, Lisa Poray, Jaime Regal, Effie Roland, Keysha Ross, Michelle Russell, Betsy Schroeder, Tricia Schwartz, Sheryl Shapiro, Theresa Sommers, and Donald Spatz; Gary Brunette, Gary Buckett, Gary Euler, Dan Fishbein, Emilia Koumans, Jennifer McQuiston, Ava Navin, David Shay, Carolyn Bridges, Sandra Dos Santos Chaves, Abigail Shefer, and Ronald Henry for their contribution to study design, thorough review, and statistical support. This work was supported solely by the US CDC.
The findings and conclusions in this report are those of the authors and do not necessarily represent the views of the Centers for Disease Control and Prevention.
Declaration of Interests
All the authors state that they have no conflicts of interest to declare.