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The World in Medicine
August 18, 2004

Deadlier Bird Flu?

JAMA. 2004;292(7):794. doi:10.1001/jama.292.7.794-a

Strains of avian influenza virus have become increasingly pathogenic to mammals, according to research published on July 2 in an online edition of the Proceedings of the National Academy of Sciences (http://www.pnas.org). The findings underscore concerns that the virus will evolve to spread more easily from person to person, setting the stage for a human pandemic.

Researchers from China and the United States inoculated chickens and mice with H5N1 bird flu isolates obtained between 1999 and 2002 from apparently healthy ducks (a natural reservoir for avian influenza). They found that the isolates were highly lethal to chickens; in mice, viruses isolated in 2001 and 2002 were significantly more pathogenic than those isolated in 1999 and 2000. An analysis of the viral isolates' genomes, they said, suggests that progressive mutations may have contributed to an increase in the strains' pathogenic potential.