The outbreak, found in Leshan, Sichuan province, on a truck transporting 111 pigs from other provinces, has killed seven of the herd, according to a statement published on the website of the Ministry of Agriculture and Rural Affairs.

The deadly disease, first detected in China in August 2018, has slashed the country's massive hog herd by almost 50 percent.

What is African swine fever?

African swine fever (ASF) resembles classical swine fever (CSF) (hog cholera) so closely that laboratory tests are required to differentiate them. The clinical signs and post-mortem lesions of the two diseases are almost indistinguishable. ASF is caused by a unique virus which is distinct from that of CSF and which infects only domestic and wild pigs and a variety of soft bodied ticks. The virus is endemic in Africa south of the equator, in warthogs and bush pigs, but the infection in them produces no clinical disease. It circulates between warthogs and the soft bodied ticks which inhabit their burrows. The ticks transmit it through all stages of their life cycle and perpetuate it. It is also endemic in the domestic pigs of some African countries.

Contamination generally occurs via direct contact with tissue and bodily fluids from infected or carrier pigs, including discharges from the nose, mouth, urine and faeces or infected semen. It also spreads through transport and consumption of contaminated food products, and some cases have originated from failure to comply with biosecurity standards by feeding waste food to domestic pigs. It is believed that a highly pathogenic strain of ASF was introduced to domestic pigs and, subsequently, wild boar populations in the port of Poti, Georgia, in 2007 when waste food from a ship originating in South Africa was fed to local pigs.

For more information on the clinical signs of African swine fever, visit our Disease Index.