By Umberto Bacchi
ROME, March 17 (Thomson Reuters Foundation) - Countries trading in Chinese poultry should step up surveillance at farms, markets and border checkpoints to prevent the spread of H7N9 bird flu from China after a more severe strain of the virus was detected in chickens, a U.N. agency said on Friday.
H7N9 has killed almost 500 people in China since it was first reported in 2013 but until recently had shown little or no clinical symptoms in birds, according to the U.N. Food and Agriculture Organization (FAO).
But in February Beijing reported it detected an evolution in the virus that caused severe disease and death in poultry within 48 hours of infection.
"It now goes beyond being primarily a public health concern," said FAO's veterinary epidemiologist Sophie von Dobschuetz, adding the new strain heightened the risk for farmers to lose animals and livelihoods.
The highly pathogenic variant has only been reported in China's southeastern Guangdong province and will become more apparent in some flocks if birds begin to die off, making detection and control easier, FAO said.
"The earlier you pick up the incursion of the virus the more chance you have to control it," von Dobschuetz told the Thomson Reuters Foundation by phone.
The new strain has raised concerns that the infection could pass from chickens to other birds, increasing the risk of it spreading across borders, the FAO said in joint statement with the World Organisation for Animal Health (OIE).
The FAO said the new H7N9 strain maintained its capacity to cause severe illness in people, but the World Health Organization said there was no evidence of changes in the virus' ability to spread between humans.
Von Dobschuetz said China was assessing the virus' prevalence and results were expected in the coming weeks.
Since the virus was first identified in 2013, 1,320 human cases have been recorded in China, including 492 deaths, according to FAO figures.
(Reporting by Umberto Bacchi @UmbertoBacchi, Editing by Ros Russell.; Please credit the Thomson Reuters Foundation, the charitable arm of Thomson Reuters, that covers humanitarian news, women's rights, trafficking, property rights, climate change and resilience. Visit http://news.trust.org)