510. Rapid assessment of severity during the 2009 H1N1 influenza pandemic: the value of epidemiologic field investigations
Session: Poster Abstract Session: Influenza and other Respiratory Viral Infections Epidemiology Studies
Friday, October 21, 2011
Room: Poster Hall B1

Background:  Early in the 2009 Influenza A (H1N1) pandemic, Mexico reported alarming case-hospitalization and fatality rates.  Rapid objective determination of the pandemic severity was critical for US control and policy decisions.  CDC deployed field teams to conduct rapid community assessments in two early US outbreaks, the University of Delaware (UD) (student population 18,872) and a highly affected Chicago neighborhood (population 38,351), to estimate the severity of the pandemic.

Methods:  At UD we conducted a university-wide on-line survey (May 10-18, 2009) and in Chicago, a door-to-door survey (May 11-17). Respondents were asked about influenza like illness (ILI) symptoms and outcomes. We reviewed area hospital and death records.  We compared ILI attack rates (AR), hospitalization and case fatality rates (CFR) to published rates from the 1918 (AR 30%, CFR 2%) and 1968 (AR 37%, CFR 0.2%) influenza pandemics projected per 10,000 population.

Results:  6049 (32%) of UD students responded to the survey.  604 (10%) reported ILI and four (0.07%) reported being hospitalized or 1000/10,000 with ILI and 6.6/10,000 hospitalized.  In Chicago 644 participants from 240 households were interviewed; 37 (5.7%) reported ILI and one (0.15%) was hospitalized, or 574/10,000 with ILI and 15.5/10,000 hospitalized.  There were no deaths reported at UD or from the Chicago community.  In contrast, in 1918 there would have been 3000/10,000 persons with ILI and 60/10,000 deaths and in 1968 3700/10,000 persons with ILI and 7.4/10,000 deaths.


Delaware: University

Chicago: Community




















Conclusion:  Within weeks of the onset of the 2009 pandemic, rapid community assessments suggested that the pandemic was mild to moderately severe-if it had been as severe as either 1918 or 1968 far more deaths would have occurred.  While these rapid assessment data were preliminary, not age adjusted, and would need re-assessment throughout the pandemic, they helped inform control policy.  Similar methodology could be used at the onset of a future influenza pandemic or disease outbreak to gauge preliminary disease severity and guide resource allocations.

Subject Category: N. Hospital-acquired and surgical infections, infection control, and health outcomes including general public health and health services research

David L. Swerdlow, MD1, A. Danielle Iuliano, PhD, MPH1, J. Erin Staples, MD, PhD2, Carrie Reed, ScD1, Matthew Biggerstaff, MPH1 and Lyn Finelli, DrPH, MS1, (1)Centers for Disease Control and Prevention, Atlanta, GA, (2)CDC, Fort Collins, CO


D. L. Swerdlow, None

A. D. Iuliano, None

J. E. Staples, None

C. Reed, None

M. Biggerstaff, None

L. Finelli, None

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