China has been battling African swine fever (ASF) since August 2018, after the disease spread rapidly throughout the world's top pork producer, killing millions of pigs and sending pork prices soaring.

In the latest incident the virus was found in pigs on a truck stopped for inspection in Nanjiang county near Bazhong city. The truck carried more than 100 pigs and two had died, the ministry said.

Cases reported by the Ministry of Agriculture and Rural Affairs had dwindled to just a couple per month by the end of last year, but 13 ASF cases have been posted on the ministry's website since March.

All of the cases, apart from one found in wild boar, were in pigs being transported between provinces.

"The government has easier access to pig transport trucks than having to rely on farmers' willingness to report outbreaks," said Dirk Pfeiffer, professor of veterinary epidemiology at City University of Hong Kong.

Pfeiffer added that the recent reports may not reveal much about the epidemiology of the disease, with reported cases likely just the tip of the iceberg.

Despite outbreak figures from the agriculture ministry suggesting far fewer animals involved, the ministry's own data showed that by September 2019 the national pig herd had shrunk 41 percent year on year. Many in the industry believe it shrunk by as much as 60 percent.

Vice agriculture minister Yu Kangzhen said on Monday that the risk of African swine fever had increased significantly recently as farmers rush to rebuild their herds and move young pigs into new farms.