USDA study finds H7N9 infections most likely sourced from quail and chicken

A recent article conducted by scientists from the United States Department of Agriculture found that avian influenza H7N9 is most likely sourced from quails and chickens, a discovery that can enhance viral control methods.

The study was led by David Suarez of the USDA and published in a recent issue of the Journal of Virology. The H7N9 influenza strain surfaced in March 2013 and has since infected approximately 375 humans, resulting in 100 deaths.

"We quickly recognized that the virus from this outbreak was unusual, and represented a real human and veterinary risk," Suarez said. "We felt a major knowledge gap in the outbreak was that we didn't know which poultry species was maintaining the virus and exposing people. With this information, better decisions can be made to control and hopefully eradicate the virus."

Researchers gathered seven species of poultry, infected them with human isolates of the H7N9 virus from China and began observing the spread of infection among each species. The team found that the virus transmitted most rapidly among quail and was nearly as successful in chickens. The other five species, including pigeons and pekin ducks, did not successfully transmit the virus.

Researchers also found that while the virus successfully spread in quail and chicken populations, the birds showed no sign of infection - making both detection and prevention increasingly difficult.

"This work supports the field epidemiology studies that had identified live poultry markets as the likely source of the outbreak," Suarez said. "The Chinese correctly closed the live bird markets where they had human infections, and that reduced the number of cases for a while. However, their efforts did not eradicate the virus and it has returned for a second wave."