New flu may not spread like regular flu

By Maggie Fox, Health and Science Editor

WASHINGTON (Reuters) - The new H1N1 influenza strain may be just a little less catching than seasonal flu, but seems a little better able to cause stomach upsets, researchers reported on Thursday.

Genetic analysis and lab experiments with the virus show it lacks a piece of genetic material that makes ordinary flu viruses so transmissible, a team of U.S. researchers found.

Researchers in the Netherlands, meanwhile, found it lives very well in the nose and their findings suggest it has the ability to stay around for a long time -- and get worse.

Both studies, published in the journal Science, show that H1N1 swine flu needs to be closely watched, said Dr. Terrence Tumpey of the U.S. Centers for Disease Control and Prevention.

"I think the take-home message is that we really need to keep a close eye on this virus," Tumpey said in a telephone interview.

Last month the World Health Organization declared a pandemic of the new swine flu. It has been confirmed in more than 77,000 people globally and has killed at least 332 people, but U.S. officials have said there are likely a million or more cases in the United States alone.

Although flu season usually ends in April in the Northern Hemisphere, the new virus is still causing widespread illness and it is actively in the mix of seasonal flu viruses now circulating during the Southern Hemisphere's winter.

Tumpey and colleagues tested samples of the new virus from a California child who recovered from a mild bout with the new flu, a Texas child who died and a Mexican woman who had severe disease.