H1N1, Seasonal Flu Have Similar Attack Rates

Also, outbreaks of pandemic flu well controlled with oseltamivir in military camps
By Lindsey Marcellin
HealthDay Reporter

THURSDAY, June 10 (HealthDay News) -- The pandemic 2009 H1N1 influenza virus had transmissibility and clinical features similar to those of seasonal influenza A viruses, and the use of oseltamivir ring chemoprophylaxis -- along with quick identification and isolation of affected individuals -- effectively reduced the impact of 2009 H1N1 outbreaks in semiclosed settings, according to two studies published in the June 10 issue of the New England Journal of Medicine.

Benjamin J. Cowling, Ph.D., of the University of Hong Kong, and colleagues conducted a prospective study of household transmission of seasonal influenza A and pandemic H1N1 in Hong Kong during the summer of 2009. Secondary attack rates among household contacts of 99 index patients were found to be similar for the seasonal and pandemic viral strains (8 and 9 percent, respectively), as were the rates of viral shedding, transmissibility, and clinical characteristics.

Vernon J. Lee, of the Ministry of Defence in Singapore, conducted a study of the use of oseltamivir ring chemoprophylaxis (geographically targeted prophylaxis) to decrease transmission of H1N1 influenza in four military camps in Singapore in the midst of outbreaks in June 2009. The number of new cases attributable to an index case fell significantly from 1.91 before the oseltamivir intervention to 0.11 after ring chemoprophylaxis using the drug. Of those receiving oseltamivir, 7.7 percent had mild, non-respiratory side effects.

"The Singapore study showed that ring chemoprophylaxis with oseltamivir was important, along with other interventions, in controlling outbreaks of 2009 H1N1 virus infection in semiclosed settings. However, the findings do not directly inform the success of potential containment efforts implemented at the source of the next influenza pandemic or implemented to prevent the introduction of influenza into a community," writes the author of an accompanying editorial.

Abstract - Cowling
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Abstract - Lee
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