Chinese H5N1 traced to live bird markets

Sequences of the H5N1 virus from live bird markets in China have matched the sequences found in patients who had recently visited the markets, providing evidence of a long suspected molecular link.

A new paper in the December issue of the Journal of Virology provides evidence that Chinese live poultry markets serve as a reservoir for human cases, according to

“We collected 69 environmental samples—basically swabs from ditches, cages, floors, water, and so on—from the live bird markets, which six individual patients visited before disease onset,” co-author Yuelong Shu said, reports. The data was collected during the 2008-2009 flu season. “Among these 69 samples, we isolated a total of 12 highly pathogenic H5N1 avian influenza viruses from four of the six live bird markets. The genetic sequence of the environmental and corresponding human isolates was similar [with a sequence identity of greater than 99 percent], demonstrating a solid link between human infection and live poultry markets."

The researchers also analyzed 31 H5N1 viruses isolated from the 38 human cases identified in China over the past five years. The viruses displayed diverse genotypes that were consistent with the poultry outbreaks seen in live poultry markets.

“Enhanced infection control measures are warranted in these markets, not only to reduce human H5N1 infection, but also to minimize the likelihood of coinfection with H5N1 and 2009 H1N1 viruses,” the report said, reports. “The sporadic cases of human H5N1 highly pathogenic avian influenza infection, the H5N1 outbreaks in birds, and the simultaneous circulation of the 2009 H1N1 pandemic virus raise concern that a deadly reassortment virus may emerge.”