First Molecular Evidence Links Live Poultry Markets to Human H5N1 Infection in China
Sequences of H5N1 virus from live bird markets in China
matched sequences from patients who had recently visited the live bird markets,
according to a paper in the December 2011 Journal
of Virology. Live poultry markets have long been suspected of providing the
reservoir of H5N1 responsible for human cases, but this is the first molecular
evidence linking H5N1 in humans to these markets, the authors say.
“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,” during the 2008-2009 flu
season, says corresponding author Yuelong Shu. “Among these 69 samples, we
isolated a total of 12 highly pathogenic H5N1 avian influenza viruses from four
of the six live bird markets.” In those cases, “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,” says Shu.
The investigators also analyzed 31 H5N1 highly pathogenic
avian influenza viruses isolated from the 38 human H5N1 cases identified in
China during the past five years, revealing “diverse genotypes… that were
consistent with those identified in poultry outbreaks or in live poultry
markets,” according to the report.
The results of this investigation have important policy
implications, says Shu. “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 researchers
write. “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.”
(X.-F. Wan, L. Dong, Y. Shu, et al. Indications that live
poultry markets are a major source of human H5N1 influenza virus infection in
China. J. Virol. 85:13432-13438.)