Science
30 October 2009  Vol 326, Issue 5953, Pages 639-737
http://www.sciencemag.org/current.dtl

Reports
The Transmissibility and Control of Pandemic Influenza A (H1N1) Virus

Yang Yang,1 Jonathan D. Sugimoto,1,2 M. Elizabeth Halloran,1,3 Nicole E. Basta,1,2 Dennis L. Chao,1 Laura Matrajt,4 Gail Potter,5 Eben Kenah,1,3,6 Ira M. Longini, Jr.1,3,*

Pandemic influenza A (H1N1) 2009 (pandemic H1N1) is spreading throughout the planet. It has become the dominant strain in the Southern Hemisphere, where the influenza season has now ended. Here, on the basis of reported case clusters in the United States, we estimated the household secondary attack rate for pandemic H1N1 to be 27.3% [95% confidence interval (CI) from 12.2% to 50.5%]. From a school outbreak, we estimated that a typical schoolchild infects 2.4 (95% CI from 1.8 to 3.2) other children within the school. We estimated the basic reproductive number, R0, to range from 1.3 to 1.7 and the generation interval to range from 2.6 to 3.2 days. We used a simulation model to evaluate the effectiveness of vaccination strategies in the United States for fall 2009. If a vaccine were available soon enough, vaccination of children, followed by adults, reaching 70% overall coverage, in addition to high-risk and essential workforce groups, could mitigate a severe epidemic.

1 Center for Statistics and Quantitative Infectious Diseases, Fred Hutchinson Cancer Research Center and the University of Washington, Seattle, WA 98109, USA.
2 Department of Epidemiology, School of Public Health, University of Washington, Seattle, WA 98195, USA.
3 Department of Biostatistics, School of Public Health, University of Washington, Seattle, WA 98195, USA.
4 Department of Applied Mathematics, University of Washington, Seattle, WA 98195, USA.
5 Department of Statistics, University of Washington, Seattle, WA 98195, USA.
6 Department of Global Health, University of Washington, Seattle, WA 98195, USA.

* To whom correspondence should be addressed. E-mail: longini@scharp.org