By Viv Robins

Authorities in Hong Kong have sealed off a pond in a public park after the discovery of five dead birds fanned fears of a new outbreak of avian flu.

The incident was the third in as many weeks, the most recent only days ago when dozens of chickens were found dead of the disease in local poultry markets.

In 1997, six people died in Hong Kong when a strain of the virus crossed the species barrier for the first time.

The authorities slaughtered thousands of chickens last year

The pond in Kowloon Park was closed after the discovery of the bodies of four ducks and a swan.

Preliminary tests on the birds suggested that they were carrying the so-called H5 avian virus.

It was a strain of this virus which made the unusual jump from birds to humans five years ago.

Mass culls

The discovery at the pond follows the deaths of 24 chickens in five poultry markets on the mainland and Lantau Island.

Health officials moved quickly then to shut down the affected premises and insist that there was no cause for concern.

However, the chicken deaths came just two weeks after two geese tested positive for avian flu out of a batch of 31 birds found dead in a waterfowl park.

The congested territory of more than six and a half million people has been hit by three major outbreaks of the flu in the last five years, each time leading to massive culls.

The risk of transmission to humans is thought to be exacerbated by poor sanitation at wholesale markets and their often close proximity to living and playing areas, together with customers' preference for having the birds slaughtered on the spot so they can be taken home as fresh as possible.