Swine flu: You may be contagious longer than you think

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Part of the public-health mantra for dealing with the H1N1 flu pandemic is the recommendation that patients remain isolated while the illness runs its course. Experts have estimated that is about seven days. Others recommend that people remain isolated for an additional 24 hours after the fever is gone (without the use of fever-reducing medication), as detailed in Monday’s L.A. Times special health section on flu. But a new study suggests that people with H1N1 flu may be contagious longer than previous suspected.

Researchers in Quebec studied 44 people across a variety of ages who had confirmed cases of novel H1N1 influenza (swine flu) last spring. On the eighth day of illness, a nasal swab was taken to check for virus levels. Among all age groups, from 45% to 75% still tested positive on flu tests, and 19% were still shedding replicating virus -- meaning germs that can infect others.

The study suggests that the isolation period for H1N1 patients is seven to 10 days, said Dr. Gaston de Serres, the lead author of the study, from Laval University in Quebec.

‘Policies on how long should people stay home are difficult,’ de Serres said. ‘With seasonal influenza, normally after a week the contagiousness is gone. H1N1 appears to be shed longer in all age groups, but not much longer. ... I think the key message here is for those who would want to stay home for just a couple of days, that is likely to be insufficient. I think this study shows you are not contagious for just a day or two but probably for a week.’

The study was presented at the Interscience Conference on Antimicrobial Agents and Chemotherapy in San Francisco.

-- Shari Roan