A genetic analysis of the avian flu virus responsible for at least nine human deaths in China portrays a virus evolving to adapt to human cells, raising concern about its potential to spark a new global flu pandemic. The collaborative study, conducted by a group led by Dr. Masato Tashiro of the Influenza Virus Research Center, National Institute of Infectious Diseases, and Dr. Yoshihiro Kawaoka of the University of Wisconsin-Madison and the University of Tokyo, appears in the April 11, 2013 issue of the journal Eurosurveillance. The group examined the genetic sequences of H7N9 isolates from four of the pathogen's human victims, as well as samples derived from birds and the environs of a Shanghai market. "The human isolates, but not the avian and environmental ones, have a protein mutation that allows for efficient growth in human cells and that also allows them to grow at a temperature that corresponds to the upper respiratory tract of humans, which is lower than you find in birds," says Dr. Kawaoka, a leading expert on avian influenza. The findings, drawn from genetic sequences deposited by Chinese researchers into an international database, provide some of the first molecular clues about a worrisome new strain of bird flu, the first human cases of which were reported on March 31, 2013, by the Chinese Center for Disease Control and Prevention. So far, the new virus has sickened at least 33 people, killing nine. Although it is too early to predict its potential to cause a pandemic, signs that the virus is adapting to mammalian and, in particular, human hosts are unmistakable, says Dr. Kawaoka. Access to the genetic information in the viruses, he adds, is necessary for understanding how the virus is evolving and for developing a candidate vaccine to prevent infection.
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