It's Possible to Come Down With Two Flu Viruses at Once

Report confirms cases of people infected by H1N1 and another flu strain at the same time

WEDNESDAY, Nov. 2 (HealthDay News) -- A rare occurrence of people becoming infected with seasonal and pandemic flu strains at the same time has been confirmed by researchers.

The co-infection with the pandemic H1N1 swine flu strain and a seasonal strain called H3N2 was identified in a young Cambodian boy and his teacher in October 2009. A complete sequencing of the genomes of both viruses showed that the viruses did not recombine into a new and different virus.

Both patients recovered, but the researchers say the event serves as a reminder of the ongoing risk of different flu viruses combining in people to create a more lethal strain. They also said that flu virus co-infections in Southeast Asia require particularly close scrutiny due to the ongoing presence of the H5N1 bird flu virus and the pandemic H1N1 virus.

The report is published in the November issue of the American Journal of Tropical Medicine and Hygiene.

"Influenza viruses are continually changing," report co-author Patrick Blair, director of respiratory diseases at the U.S. Naval Health Research Center in San Diego, said in a news release from the American Society of Tropical Medicine and Hygiene. "Finding a co-infection in an area where there is considerable seasonal flu, pandemic flu and H5N1 avian flu shows there is an opportunity for co-mingling in swine or human hosts that could create an ominous global health problem."

Flu virus co-infections are rare. Other researchers looking for co-infections involving the pandemic H1N1 virus found only one in Singapore, six in China and 11 in New Zealand.

Scientists and public health officials are particularly worried about potential co-infections involving the H5N1 bird flu virus, against which humans have little immune defense. There have been 566 known human infections with H5N1 and 332 of those people have died, a death rate of more than 60 percent, according to the World Health Organization.

So far, the H5N1 virus has shown a very limited ability to pass from person to person. Most of the human infections have been caused by direct contact with infected poultry and other birds.

But a co-infection involving the H5N1 virus and a seasonal flu virus that leads to a new H5N1 strain that could more easily pass between humans could pose a serious threat worldwide, the researchers suggested in the news release.

More information

The World Health Organization has more about influenza.

-- Robert Preidt

SOURCE: American Society of Tropical Medicine and Hygiene, news release, Nov. 2, 2011

Last Updated: Nov. 02, 2011

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