Fear of a bird flu pandemic has led to the slaughter of 17,000 chickens in Hong Kong on Wednesday, after an infected carcass was discovered at a poultry market. Officials have yet to determine if the infected bird was imported or from a local source.

The market was closed and the import or sale of live poultry has been halted for three weeks.

The H5N1 avian flu virus is normally found in birds, but can jump to humans. It is highly lethal – it kills most birds and 60 percent of people infected.

The first major outbreak of H5N1 among humans occurred in Hong Kong in 1997, when it killed six people. As a result, the government killed 1.4 million birds in an effort to contain the virus. The territory also went through a Severe Acute Respiratory Syndrome (SARS) outbreak in 2003 that killed 299 people.

“We have to be very cautious,” said K.Y. Yuen, chairman of the microbiology department at the University of Hong Kong. “But there is no need for panic.”

Since 2003, 573 people worldwide have been infected with H5N1, and 336 have died, according to the World Health Organization.