WIKIMEDIA, GAVIN SCHAEFERThe avian influenza virus H9N2, which helped give rise to the deadly H7N9, evolved to become increasingly infectious in chickens in the years leading up to H7N9’s emergence, according to a paper published yesterday (December 29) in PNAS. H9N2 has been circulating on chicken farms in China since 1994. In recent years, the virus recombined in poultry markets with H7 and N9 viruses that had been passed from wild birds to domestic ducks. The resulting H7N9 flu virus jumped to humans in 2013, and by October 2014 had killed 175 of the 453 people it had infected, according to the World Health Organization. This latest viral analysis sheds light on the genetic changes to H9N2 that may have made H7N9’s emergence possible.
“[The] study reveals the increased H9N2 prevalence in poultry farms in China, due to the emergence of a more infectious and antigenically distinct H9N2 genotype,” Tommy Tsan-Yuk Lam of the University of Hong Kong’s School of Public Health, who was not involved in the study, wrote in an e-mail to The Scientist. “This might partly explain by H7N9 virus chose the H9N2 virus to reassort with.”
“With the combination of vaccine-driven selection and reassortment going on, you got the precursor of the H9N2 that was optimal for complementing H7N9 and going into humans,” said study coauthor Robert Webster of St. Jude Children’s Research Hospital in Memphis, Tennessee.
Webster and his colleagues collaborated with the lab of Jinhua Liu at China Agricultural University in Beijing, which ...
