Hong Kong authorities responded to fears of a dangerous bird flu outbreak and announced the decision to kill all poultry in the city’s markets and retail outlets. The order does not affect sales of pre-slaughtered poultry sold packaged in supermarkets. It does not apply either to Hong Kong’s chicken farmers because samples taken from local farms have so far tested negative. But Hong Kong residents use to buy live chickens and prepare them for cooking at home.  

Scientists have warned that the virus could mutate into a form that would pass from human to human, which may lead to an epidemic.

Authorities detected one of the largest outbreaks of the bird flu virus in the years.

Last year, in early September, a bird flu outbreak in south China’s Guangzhou led to the death of more than 9,000 ducks. Then, the National Avian Influenza Reference Laboratory confirmed the outbreak as a sub-type of H5N1 bird flu and the government has culled more than 50,000 fowls in the infected region.

The deadly virus H5N1 was detected last week in chickens at a stall in the Kowloon area. Authorities slaughtered about 2,700 animals in the area to prevent its spread. The virus was also detected at four markets in the New Territories and Hong Kong Island.

No humans are known to have been infected in the current outbreak, the officials said.

“We are closely monitoring the possibility of human cases, and we will remain alert,” Thomas Tsang, a senior health official, told the Associated Press.

About 3,500 more birds will have to be slaughtered in the several hundred shops and stalls that sell live poultry, according to Reuters. The chickens will be pulled from cages, slaughtered and placed in bags filled with disinfectant powder. Poultry trade across the country must also be secured.

“We are working on finding the origin of this virus but have had no result yet,” said Sally Hong, a spokeswoman for the Agriculture, Fisheries and Conservation Department, according to the same source.

“We cannot be complacent and that is why we are taking this decisive measure to close all retail outlets and to cull all remaining live poultry,” Cheung Siu-hing, director for agriculture, fisheries and conservation, said at a news conference.