Influenza A: Infection possible even 8 days after fever

Two new studies conducted by the U.S. scientists could be significant on the spread of the virus. Some people infected with the H1N1 virus might indeed be contagious one week or more after the disappearance of fever, longer than was thought before.

The results of these two studies, one conducted in Canada, the another in Singapore, come to similar conclusions. According to them, 19 to 30% of infected people could be contagious up to eight days or more after the disappearance of the fever.

"This study shows that a person can be infectious not only 24 or 48 hours but possibly up to a week after the disappearance of the fever, " said Dr. Gaston De Serres from the  Institut National Public Health of Quebec (Canada) at a press conference after the 49th Annual Conference on Antimicrobial Agents and Chemotherapy (ICAAC) meeting in San Francisco (California).

Of the 43 patients infected by the H1N1 virus and observed for this study, 8 of them still had live virus in their blood that can multiply and thus make the person contagious eight days after the fever. After ten days, none of these patients showed any trace of H1N1 in the analysis of viral cultures.

The second e study conducted by Dr David Lye of Tan Tock Seng Hospital in Singapore on 70 patients with influenza H1N1 has shown that 20 to 30% were still carrying live virus, and therefore potentially contagious after eight days, until twelve days. For patients treated with antivirals, the infectious period was shorter.

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