When the coughing stops is probably a better sign of when a swine flu patient is no longer contagious, experts said after seeing new research that suggests the virus can still spread many days after a fever goes away.
The federal Centers for Disease Control and Prevention has been telling people to stay home from work and school and avoid contact with others until a day after their fever breaks. The new research suggests they may need to be careful for longer – especially at home where the risk of spreading the germ is highest.
Swine flu also appears to be contagious longer than ordinary seasonal flu, several experts said.
"This study shows you're not contagious for a day or two. You're probably contagious for about a week," said Gaston De Serres, a scientist at the Institute of Public Health in Quebec.
He presented one of the studies Monday at an American Society for Microbiology conference. It is the first big meeting of infectious disease experts since last spring's emergence of swine flu, which now accounts for nearly all of the flu cases in the United States.
More than 1 million Americans have been infected and nearly 600 have died from it, the CDC estimates.
It is unclear whether the new research will lead the CDC to rethink its advice on how long people with swine flu should hole up. Long breaks from school and work do not seem worth it for a virus that now seems to cause mostly mild illness, said the CDC's flu chief, Nancy Cox. Swine flu is spreading so widely now that confining the sick does less good, she said.