"The woman died early on Christmas Day and tested positive for bird flu," said Muhammad Nadhirin, an official with the Health Ministry's bird flu information center. It is not yet known how she contracted the virus. There have been five other bird-flu deaths in Indonesia since October, making it the hardest hit country with 94 deaths.

According to a Hong Kong pathologist, there is evidence of a few clusters of human-to-human transmission when looking at the past decade of bird-flu incidents in Asia.

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"It is limited to close contact with the patient, like prolonged exposure from family members caring for the infected," said pathologist Samson Wong Sai-yin of Hong Kong University's department of microbiology.

"It can happen and no one doubts it but the good thing is that it is still not easily transmitted like human influenza," Wong added.

From the experience of the past few years, cases of bird flu are most common during winter, especially in the mainland coastal areas, he said.

While human-to-human cases may be possible, infection by wild birds and poultry or the domesticated variety is still the most common source for human infection, according to Wong.

Locally, a buzzard - a common migratory bird that winters in Hong Kong - tested positive for avian flu after it was found dead on Lantau on December 17.

A grey heron found near the Lok Ma Chau MTR station on December 5 also died of H5N1 a day later, prompting the closing of the Mai Po nature reserve for three weeks by the Agricultural, Fisheries and Conservation Department.

Although the threat from avian flu will subside as summer approaches, the Southeast Asian region will remain prone to sporadic cases of H5N1 due to their more stable temperatures, according to Wong.

But in places like Indonesia, there are no clear- cut seasons.

Hong Kong's proximity to hotzones such as Indonesia means the monitoring of poultry has to remain vigilant, said Wong.