The government has ordered the slaughter of about 240 pigs at a farm in Yuen Long after six animals tested positive for the African swine fever virus that reached epidemic levels on the mainland in 2019.

The virus is harmless to humans and is not considered a threat to food safety but spreads fast among swine populations and often proves deadly.

The Agriculture, Fisheries and Conservation Department said it took action under its African swine fever contingency plan after six pigs in one shed at a farm in Wong Nai Tun tested positive on Thursday.

It ordered the culling of all 240 pigs in the same shed, but tests on pigs elsewhere on the farm proved negative.

“Given the fact that there is stringent biosecurity measures implemented on the farm to minimise the risk of infection, and that all sheds are separated structures without any linkage in between, further observation and testing are considered appropriate without the necessity of culling any pigs in other sheds at this stage after consulting international experts in the area,” a department spokesman said.

“Thorough cleansing and disinfection is being conducted on the farm.”

Department staff have also checked on three other farms within three kilometres and found no abnormalities. It’s suspended movement of pigs on nearby farms and will take samples to check for infection.

Since the major outbreak on the mainland in 2019, which saw more than 100 million animals culled or die of the disease, Hong Kong has implemented stringent biosecurity measures, including cleansing and disinfection of vehicles going to the Sheung Shui Slaughterhouse.

The department said there was no need for the slaughterhouse to close or for more pigs to be culled.

The first case of the fever in Hong Kong forced the culling of 6,000 pigs in May 2019.