Reported cases of H7N9 infections in China have slowed after the restriction of live poultry sales in cities with the most reported infections, with no new cases in Shanghai since April 13, a week after the markets were ordered to be shut, according to the World Health Organization Collaborating Center for Reference and Research on Influenza.  Markets were also closed in Nanjing and Hangzhou.  The H7N9 virus appeared to first emerge in February in China.

The cumulative number of reported cases is plateauing, now at 129 cases, with 26 fatalities. The slowing of reported cases suggest that the virus can be controlled by slaughtering poultry and disinfecting markets, as well as programs of surveillance, culling, improved biosecurity, segregation of different poultry species, and possibly vaccination programs to control H7N9 virus infections in poultry.   “This really does suggest that closing down the live bird markets has reduced the risk of infection,” said Ann Kelso, director of a World Health Organization flu research center in Melbourne, who is among a number of international specialists invited to China to advise the government on bird flu.

A joint team of doctors from China and the World Health Organization this week reported that  77 percent of the documented cases were in people who had either visited live animal markets, or had some sort of contact.  The researchers looked at the genetic sequence of four patients–two of who had died.  One was a chef who prepared chicken, another had slaughtered poultry from one of the markets, and two had bought live birds from wet markets.  The genetic sequences from the men very closely resembled virus taken from poultry at the markets they had visited or prepared chickens from.

“Overall, the evidence, in terms of epidemiology and virology, suggest that it is a pure poultry to human transmission, and that controlling the epidemic in humans will therefore depend on controlling the epidemic in poultry,” Kwok-Yung Yuen of the University of Hong Kong, said in a statement this week.

Meanwhile, USDA has set up a Situational Awareness Coordination Unit with a core team of experts and other USDA representatives, including the Animal and Plant Health Inspection Service (APHIS), the Agricultural Research Service (ARS), the Food Safety and Inspection Service, and the Foreign Agricultural Service.  USDA and the Chinese Center for Disease Control and Prevention are collaborating to understand  the epidemiology of H7N9 infections among humans and animals in China.

In addition, APHIS is working with the U.S. Department of the Interior to assess evidence for potential movement of Eurasian avian influenza viruses into North America via wild birds.   ARS has also completed a preliminary antigenic mapping study to help identify virus isolates that could be used to develop a vaccine for poultry if needed.