It doesn't pose a risk to human health, people should not be too worried

Environment and Food Secretary Lily Yam

Environment and Food Secretary Lily Yam said 1.2 million birds would be slaughtered.

But she added that the virus was different to the 1997 strain, which killed six people, and would not affect humans.

The precautionary slaughter of 4,500 chickens began on Wednesday.

The infection is a new and highly virulent strain of avian flu.

In the first 24 hours, it killed almost 800 chickens, kept in cages in three separate markets.

Now all the chickens, ducks, geese and quail in the territory's markets, along with all mature poultry on its farms, will be slaughtered at a cost of over $10m.

Demand falls

Since Wednesday, the disease has been discovered in 10 different places.

Officials hope to contain the outbreak

And demand for chickens in the territory has dropped dramatically, with scared consumers switching to other meats or vegetables.

Hong Kong consumes about 100,000 fresh chickens a day, and imports 70% of its poultry from China.

The appearance of the H5N1 virus in Hong Kong in humans in 1997 prompted fears of a worldwide epidemic.

And a 1998 study showed similarities between the virus and Spanish flu, an outbreak of which killed between 20 and 40 million people in 1918.

A less serious strain infected two children in 1999, and there were unconfirmed reports of further cases in China's southern provinces.

Most bird flu viruses do not replicate efficiently in humans.