In June 2021, a fattening pig weighing about 80 Kg showed paralytic symptoms in a farm in Shandong province. The pig was euthanized and examined in an autopsy by the Chinese National African Swine Fever Para-reference Laboratory (CNASFPL) for ASFV detection.

On another farm in Henan province, fattening pigs developed signs of chronic infection, including weight loss, intermittent fever, skin ulcers, and arthritis. Sporadic deaths were also noted. Samples from four dead pigs, including lymph nodes and spleens, were collected and delivered to the CNASFPL for ASFV detection.

All samples were found to be ASFV positive. Further sequence analysis indicated that the ASFVs in these samples belonged to genotype I.

Phylogenetic analysis of the whole genome sequences suggested that both isolates share high similarity with NH/P68 and OURT88/3, two genotype I ASFVs isolated in Portugal in the last century.

The emergence of genotype I ASFVs will present more problems and challenges for the control and prevention of African swine fever in China, concluded the paper's authors.