Lipsitch, Marc, Lajous, Martin, O'Hagan, Justin J., Cohen, Ted, Miller, Joel C., Goldstein, Edward, Danon, Leon, Wallinga, Jacco, Riley, Steven, Dowell, Scott F., Reed, Carrie and McCarron, Meg. (2009) Use of cumulative incidence of novel influenza A/H1N1 in foreign travelers to estimate lower bounds on cumulative incidence in Mexico. PL o S One, Vol.4 (No.9). ISSN 1932-6203

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Abstract

Background: An accurate estimate of the total number of cases and severity of illness of an emerging infectious disease is required both to define the burden of the epidemic and to determine the severity of disease. When a novel pathogen first appears, affected individuals with severe symptoms are more likely to be diagnosed. Accordingly, the total number of cases will be underestimated and disease severity overestimated. This problem is manifest in the current epidemic of novel influenza A/H1N1. Methods and Results: We used a simple approach to leverage measures of incident influenza A/H1N1 among a relatively small and well observed group of US, UK, Spanish and Canadian travelers who had visited Mexico to estimate the incidence among a much larger and less well surveyed population of Mexican residents. We estimate that a minimum of 113,000 to 375,000 cases of novel influenza A/H1N1 have occurred in Mexicans during the month of April, 2009. Such an estimate serves as a lower bound because it does not account for underreporting of cases in travelers or for nonrandom mixing between Mexican residents and visitors, which together could increase the estimates by more than an order of magnitude. Conclusions: We find that the number of cases in Mexican residents may exceed the number of confirmed cases by two to three orders of magnitude. While the extent of disease spread is greater than previously appreciated, our estimate suggests that severe disease is uncommon since the total number of cases is likely to be much larger than those of confirmed cases.

Item Type:	Journal Article
Subjects:	R Medicine > RA Public aspects of medicine
Divisions:	Faculty of Science > Life Sciences (2010- ) > Biological Sciences ( -2010)
Library of Congress Subject Headings (LCSH):	H1N1 influenza -- Transmission -- Mexico, H1N1 influenza -- Epidemiology, Travelers -- Mexico
Journal or Publication Title:	PL o S One
Publisher:	Public Library of Science
ISSN:	1932-6203
Date:	9 September 2009
Volume:	Vol.4
Number:	No.9
Identification Number:	10.1371/journal.pone.0006895
Status:	Peer Reviewed
Access rights to Published version:	Open Access
Funder:	National Institutes of Health (U.S.) (NIH), Consejo Nacional de Ciencia y Tecnología (Mexico) [Mexican Council for Science and Technology] (CONACYT), Mexico. Secretaría de Salud [Ministry of Health], Harvard University. Dept. of Epidemiology, United States. Dept. of Homeland Security. Science and Technology Directorate, Medical Research Council (Great Britain) (MRC), Hong Kong
Grant number:	5U01GM076497 (NIH), NIH R01 TW008246-01 (NIH)
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URI:	http://wrap.warwick.ac.uk/id/eprint/4427

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