Alarm over a sixth death from a strain of lethal bird flu never before seen in humans has led Chinese authorities to slaughter more than 20,000 birds at a poultry market in Shanghai.
The city stopped sales of live fowl and slaughtered all poultry at the market after the virus was detected in pigeons being sold for meat.
With stock markets taking fright, medical experts said the outbreak demonstrated global vulnerability to a new disease.
However, the World Health Organisation (WHO) insisted there was no evidence of "sustained human-to-human transmission" while awaiting laboratory tests on a further two deaths suspected to have been caused by the virus.
Sixteen cases of infection with the H7N9 strain have been confirmed by the WHO in the last week and 520 people who have been in close contact with confirmed victims are being closely monitored.
Alan Hampson, an influenza expert and chair of the Australian Influenza Specialist Group, said the reports were "concerning".
He added: "There is a virus out there that appears to be causing serious illness, but how widespread that illness is at this early stage we don't know.
"If a virus starts to transmit among humans then there's no telling how quickly it might travel. Does it have pandemic potential? Yes. If it learns to spread in humans, then it's a high likelihood it will become pandemic." (© Independent News Service)