Dr Margaret Chan Fung Fu-chun, formerly Hong Kong's director of health, also said that the regional culture of eating fresh chicken would have to evolve to help governments fight the diseases, reports the South China Morning Post.

In her keynote address on infectious diseases delivered in Hong Kong yesterday at a conference on investment in Asia, Dr Chan said that so far there was no global pandemic of H5N1 and H7N9 bird flu. But she warned of the "amazing ability" the viruses had to mutate, making them harder to control.

Unsustainable food production methods, such as overcrowding livestock, have been contributing to the spread of infectious diseases. Wet markets in particular have become breeding grounds for new strains of viruses and hotspots for infection, Dr Chan said.

When asked whether the government should halt live poultry sales here, she said it was an idea it "should consider".

Wet markets selling live poultry are not common in many parts of the world, but in Hong Kong and parts of southern Asia there is still an appetite for fresh chicken, she said. "You can't just blame the government."

Dr Chan said she believes the Hong Kong government is trying to encourage a change in that culture.

WHO has been monitoring occurrences of diseases in different parts of the world, including analysing online posts to search for rumours and early indications of an outbreak, she said.

In her talk, she also stressed the importance of tackling the rise of antibiotic-resistant "superbugs".

"There are far too many people who expect doctors to prescribe antibiotics." Recalling her experience treating patients, she said: "It's easier to make a prescription than to explain [the problem] to the patient, but that has to change."

With more bacteria becoming resistant to antibiotics, hospitals have become hotbeds of bacterial infection, she said. If the current trend continues, the world may be going back to a period when no effective drugs are available to treat infections, Dr Chan warned.

"If that happens, even simple surgery like laser treatment for myopia would be too dangerous," she said.