Asian governments should not let down their guard against bird flu, as the new outbreak in Hong Kong shows the disease still poses a threat, according to a World Health Organisation (WHO) official.

Hong Kong authorities have responded well by suspending poultry imports for three weeks and beginning the culling of 80,000 birds after three chickens found dead at a farm on Monday (Dec 8) tested positive for the H5 virus group, said Shigeru Omi, WHO Western Pacific Director.

Further tests are being conducted to see if the dead chickens were infected with the deadly H5N1 strain. 

Omi said the outbreak in Hong Kong was not unexpected as the virus continues to circulate around the world, especially in Asia.

Constant vigilance is the key, Omi said.

About 20 countries had bird flu outbreaks in the first three quarters of 2008, down from 25 in the same period last year, UN officials said.