Influenza-Like Illness in the Community during the Emergence of 2009 Pandemic Influenza A(H1N1) - Survey of 10 States, April 2009

Influenza Division, Centers for Disease Control and Prevention, Atlanta, Georgia 30333, USA.
Clinical Infectious Diseases (Impact Factor: 8.89). 01/2011; 52 Suppl 1(Supplement 1):S90-3. DOI: 10.1093/cid/ciq024
Source: PubMed


Following the emergence of 2009 pandemic influenza A(H1N1) virus (pH1N1) in the United States, the incidence of pH1N1 in the
community was unclear, because not all persons with influenza come to medical attention. To better estimate the incidence
of pH1N1 in the community early in the pandemic, a telephone survey was conducted in 10 states. The community incidence of
influenza-like illness in April 2009 was 4.7 per 100 adults (95% confidence interval: 2.8-6.6); half of adults reported seeking
medical care for their illness. Such surveys may be important tools for assessing the level of illness in the general population,
including those who do not seek medical care and are thus not captured using traditional surveillance methods.

Download full-text


Available from: Matthew Biggerstaff
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: In April 2009, the Centers for Disease Control and Prevention confirmed 2 cases of 2009 pandemic influenza A (H1N1) virus infection in children from southern California, marking the beginning of what would be the first influenza pandemic of the twenty-first century. This report describes the epidemiology of the 2009 H1N1 pandemic in the United States, including characterization of cases, fluctuations of disease burden over the course of a year, the age distribution of illness and severe outcomes, and estimation of the overall burden of disease.
    Full-text · Article · Jan 2011 · Clinical Infectious Diseases
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Google Flu Trends (GFT) uses anonymized, aggregated internet search activity to provide near-real time estimates of influenza activity. GFT estimates have shown a strong correlation with official influenza surveillance data. The 2009 influenza virus A (H1N1) pandemic [pH1N1] provided the first opportunity to evaluate GFT during a non-seasonal influenza outbreak. In September 2009, an updated United States GFT model was developed using data from the beginning of pH1N1. We evaluated the accuracy of each U.S. GFT model by comparing weekly estimates of ILI (influenza-like illness) activity with the U.S. Outpatient Influenza-like Illness Surveillance Network (ILINet). For each GFT model we calculated the correlation and RMSE (root mean square error) between model estimates and ILINet for four time periods: pre-H1N1, Summer H1N1, Winter H1N1, and H1N1 overall (Mar 2009-Dec 2009). We also compared the number of queries, query volume, and types of queries (e.g., influenza symptoms, influenza complications) in each model. Both models' estimates were highly correlated with ILINet pre-H1N1 and over the entire surveillance period, although the original model underestimated the magnitude of ILI activity during pH1N1. The updated model was more correlated with ILINet than the original model during Summer H1N1 (r = 0.95 and 0.29, respectively). The updated model included more search query terms than the original model, with more queries directly related to influenza infection, whereas the original model contained more queries related to influenza complications. Internet search behavior changed during pH1N1, particularly in the categories "influenza complications" and "term for influenza." The complications associated with pH1N1, the fact that pH1N1 began in the summer rather than winter, and changes in health-seeking behavior each may have played a part. Both GFT models performed well prior to and during pH1N1, although the updated model performed better during pH1N1, especially during the summer months.
    Full-text · Article · Aug 2011 · PLoS ONE
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Vaccination of healthcare workers (HCWs) was made a high priority during the phase six pandemic of the novel influenza A H1N1 (pH1N1) virus. We surveyed adherence to pH1N1 vaccination and the incidence of pH1N1 infection between vaccinated and unvaccinated HCWs. Employees at the S. João Hospital in Porto, Portugal, were offered pH1N1 vaccinations free of charge. Pandemrix(®) was the vaccine administered. As part of the pandemic plan, employees with influenza-like symptoms (ILS) were called upon to take an RT-PCR H1N1 test. If the test results were positive, they had to stay off work for at least 7 days. Sociodemographic data, vaccination status, contact with infectious patients, ILS and pH1N1 test results were documented in a standardised manner. The survey population comprised 5,592 employees. The vaccination rate was 30.8% (n = 1,720) for pH1N1 and 50.4% (n = 2,819) for the 2009/2010 seasonal trivalent inactivated influenza vaccine (TIV). One mild anaphylactic reaction occurred after pH1N1 vaccination. Minor local side effects occurred more often after pH1N1 vaccination than after 2009/2010 seasonal TIV (38.0% vs. 12.3%). Pandemic H1N1 infection was diagnosed in 97 HCWs (1.7%). Compared to employees with no regular patient contact, nurses (2.8%) had the highest risk of pH1N1 infection (adjusted OR 3.8; 95% CI 1.2-6.8). Vaccination reduced the pH1N1 infection risk (OR 0.12; 95% CI 0.05-0.29). Vaccine effectiveness was 90.4% (95% CI 73.5-97.3%). Vaccination reduced the pH1N1 infection risk considerably. The pandemic plan to contain the pH1N1 infection was successful. Nurses had the highest risk of pH1N1 infection and are therefore a target group for vaccination measures.
    Full-text · Article · Nov 2011 · International Archives of Occupational and Environmental Health
Show more