why was the 2009 influenza pandemic in england so small为什么2009年流感大流行在英国那么小呢.pdf

Why Was the 2009 Influenza Pandemic in England So Small? Ruben J. Kubiak*, Angela R. McLean Institute for Emerging Infections, Oxford Martin School, Department of Zoology, University of Oxford, Oxford, United Kingdom Abstract The ‘‘Swine flu’’ pandemic of 2009 caused world-wide infections and deaths. Early efforts to understand its rate of spread were used to predict the probable future number of cases, but by the end of 2009 it was clear that these predictions had substantially overestimated the pandemic’s eventual impact. In England, the Health Protection Agency made announcements of the number of cases of disease, which turned out to be surprisingly low for an influenza pandemic. The agency also carried out a serological survey half-way through the English epidemic. In this study, we use a mathematical model to reconcile early estimates of the rate of spread of infection, weekly data on the number of cases in the 2009 epidemic in England and the serological status of the English population at the end of the first pandemic wave. Our results reveal that if there are around 19 infections (i.e., seroconverters) for every reported case then the three data-sets are entirely consistent with each other. We go on to discuss when in the epidemic such a high ratio of seroconverters to cases of disease might have been detected, either through patterns in the case reports or through even earlier serological surveys. Citation: Kubiak RJ, McLean AR (2012) Why Was the 2009 Influenza Pandemic in England So Small? PLoS ONE 7(2): e30223. doi:10.1371/journal.pone.0030223 Editor: Alessandro Vespignani, Northeastern University, United States of America Received September 28, 2011; Accepted December 14, 2011; Published February 10, 2012 Copyright: 2012 Kubiak, McLean. This is an open-access article distributed under