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Volume 15, Number 12—December 2009

Dispatch

Estimates of the Prevalence of Pandemic (H1N1) 2009, United States, April–July 2009

Carrie ReedComments to Author , Frederick J. Angulo, David L. Swerdlow, Marc Lipsitch, Martin I. Meltzer, Daniel Jernigan, and Lyn Finelli
Author affiliations: Centers for Disease Control and Prevention, Atlanta, Georgia, USA (C. Reed, F.J. Angulo, D.L. Swerdlow, M.I. Meltzer, D. Jernigan, L. Finelli); Harvard School of Public Health, Boston, Massachusetts, USA (M. Lipsitch)

Main Article

Table 1

Model parameters and sources of data included in the model estimating prevalence of pandemic (H1N1) 2009, United States, April–July 2009*

Parameter Observed value Source Ranges included in the model, %
Not hospitalized Hospitalized
A Proportion of persons with influenza who seek medical care, % 42 2007 BRFSS, 9 states† 42–58 100
52–55 2009 ILI survey, 10 states†
49–58 Delaware university survey
52 Chicago community survey
B Proportion of persons seeking care with a specimen collected, % 25 2007 BRFSS, 9 states† 19–34 40–75
22–28 2009 ILI survey, 10 states†
19–34 Delaware university survey
C Proportion of specimens collected that are sent for confirmatory testing, % 26 
(through May 3) Delaware university survey 20–30 (through May 12); 5–15 (after May 12) 50–90
D Test detects influenza Published studies 90–100 90–100
E
Proportion of confirmed cases reported to CDC

Assumption
95–100
95–100
No. reported cases 43,677 Reports to CDC through July 23, 2009 4,759 (through May 12); 33,909 (after May 12) 5,009

*BFRSS, Behavioral Risk Factor Surveillance Survey; ILI, Influenza-like illness; CDC, Centers for Disease Control and Prevention. States include California, Colorado, Connecticut, Georgia, Maryland, Minnesota, New Mexico, New York, Oregon, and Tennessee.
†Parameter estimates and sources are described in further detail in the Technical Appendix.

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