The first African swine fever outbreak in China forced local authorities to destroy an initial 336 pigs to prevent the virus from infecting other pigs.
The World Organisation for Animal Health (OIE) said the outbreak was the first for such swine disease in China.
The notification on the OIE website said the outbreak in Shenyang, the capital of the northeastern Liaoning province, began on Wednesday and was ongoing.
African swine fever (ASF) is not harmful to humans but causes haemorrhagic fever in domesticated swine and wild boar that almost always ends in death within a few days.
There is no antidote or vaccine, and the only known method to prevent the disease from spreading is a mass cull of the infected livestock. The report said 47 pigs had died from the disease and another 336 exposed animals had been put down and disposed of.
The report, made by the China Animal Disease Control Centre under the Agriculture Ministry, listed the origin of the infection as being unknown or inconclusive.
It said an emergency plan had been launched and control measures taken, including setting up a quarantine zone and disinfection.
The UN Food and Agriculture Organization (FAO) warned in May of the risk of the spread of African swine fever from Russia.
China is a major producer and consumer of pork. Around half of the world’s pigs are raised in China, and the Chinese are the biggest consumers of pork per capita, according to the FAO.