Avian influenza in China is once again having a more wide-ranging effect than simply harming poultry production, and there are heightened concerns that this impact could spread beyond the country’s borders.

Human cases of infection with the H7N9 virus have surged since the end of last year and, as of early March, the country had reported more cases of human infection with influenza A (H7N9) than all of those caused by other types avian influenza virus combined.

The virus continues to infect the human population, and is still resulting in mortalities. Two more deaths were reported on March 17, while four were reported between March 10 and 16. Since 2013, there have been more than 1,300 cases of human infection with the virus strain, and the number of infected patients continues to rise on an almost daily basis.

China has upped surveillance and restricted access to live bird markets over recent years, and this latest wave of infections has prompted the government to strengthen its efforts. However, despite these restrictions, most patients have reported a history of visiting live bird markets or coming into contact with infected birds, notes the Food and Agriculture Organization. The human crisis continues.

What has made surveillance for the virus particularly challenging is that, until recently, it has caused no or few signs of disease in chickens.

Increasingly deadly for poultry

New evidence from China’s Guangdong Province, however, indicates that H7N9, while retaining its capacity to cause severe disease in humans, has shifted to high pathogenicity in poultry – a genetic change that can lead to high mortality for birds within 48 hours of infection.

The change may make it easier to see when chickens are infected and to mount an appropriate response, but raises the risk of severe bird and economic losses for those engaged in poultry production and sales.

Heightened concern over spread

There are growing concerns that the strain will not be simply a problem in China for much longer. Influenza A (H7N9) is now considered endemic in the country’s Eastern and Southeastern regions, and there are growing fears that it will spread to neighboring countries and to all those that have poultry trade connections -- either formal or informal.

A further concern is that the possibility that changes seen in the H7N9 virus may affect wild bird populations, posing risks to their health or turning them into migratory carriers of the virus, expanding the risk of the virus spreading further.

Mutations are being closely monitored in China, and the OIE’s deputy director general Matthew Stone was warned that it is essential national veterinary services conduct constant surveillance of the various virus strains that may be circulating to protect animal and human populations, and that surveillance data must be shared in a timely fashion with the international community.