The avian influenza virus H7N7 (genetically close to the H7N9 virus), has been found in Chinese live poultry markets. Medical experts suspect that this is one route of transmission for the disease between birds.
A research report published in the journal Nature summarizes the results of analyses of viral samples collected from poultry markets in China. The results indicate that some Chinese birds may have also been infected with the virus H7N7. The H7N7 virus is very closely related to the strain of 'bird flu' that has infected people (the H7N9 strain). While there have been no documented human infections related to H7N7 in China to date, the researchers were able to infect ferrets (animals that are often used as substitutes for humans) with the virus.
In April 2013, Nature News reports, researchers took throat and cloacal samples from 1,341 chickens, ducks, geese, and other birds. In addition, the scientists collected more than 1,000 fecal and water samples from live poultry markets, wetlands, and farms. The conclusion was that many birds found in live poultry markets were infected.
Study coauthor Yi Guan, a flu researcher at the University of Hong Kong, told The Guardian that the Chinese authorities should consider closing live poultry markets: "Moving live poultry markets out of urban areas may reduce the frequency of contact between infected birds or contaminated environments and humans, but there is a range of interventions that could reduce the risks of these markets being hubs for transmission and reservoirs of infection."
The avian influenza virus H7N9 infected more than 130 people in China, causing more than 40 deaths. Chinese scientists later confirmed that the avian flu virus H7N9 can spread through the air; and it can possibly be transmitted from human to human.
Interestingly, the report also suggests that 'bird flu' originated in ducks before spreading to chickens.