Porcine postweaning multisystemic wasting syndrome (PMWS) caused by porcine circovirus type 2 (PCV2) is a disease causing severe economic losses annually worldwide to the pig industry. PCV2 infection was first reported in China in 2000, and currently has three major genotypes, PCV2a, b and d, circulating in this country. To further elucidate the origin and prevalence of PCV2 in China, 123 clinical pig tissue samples collected in 25 provinces between 1990 and 1999 were analysed by PCV2-specific PCR, resulting in identification of 23 PCV2 strains collected between 1996 and 1999. Phylogenetic analysis based on the nucleotide sequences of open reading frame 2 (ORF2) showed that 20 of the 23 grouped within PCV2a, while the remaining three strains formed an independent clade, so far unreported and therefore named PCV2f. This genotype shared lower sequence identity with other known genotypes. This study provides further understanding of the genetic diversity and evolution of PCV2 and has tracked PCV2 infection in China back to 1996 rather than 2000.

PCV3 is an emerging swine virus associated with porcine dermatitis and nephropathy syndrome (PDNS), reproductive failure, respiratory diseases and systematic inflammation. Although first identified in 2015, the earliest case has been traced back to 2009 in the United States. In China, PCV3 infection was first detected in 2015, but little information has been available about its occurrence and prevalence there before 2015. In this study, 200 porcine clinical samples collected from 20 provinces, five autonomous regions and four municipalities between 1990 and 1999 were analysed for PCV3 infection by PCR. Results showed that 6.5% of the porcine samples collected from eight provinces and one autonomous region were PCV3 positive, with the earliest cases occurring in 1996. Nucleotide sequence analysis showed that PCV3 strains obtained in this study shared 96.6%-99.7% and 97.1%-99.4% sequence identity at the ORF2 gene and genome levels with all available reference strains from China and other countries, indicating the high genetic stability of PCV3 over the past 20 years.

Getah virus (GETV) is a mosquito‐borne virus that is widely distributed in Asian countries including China, in which the first case of equine GETV infection was reported in Guangdong province in August 2018. In this study, GETVs were detected in two classical swine fever virus‐positive samples collected from swine herds in Foshan city, Guangdong province, 2018. Infection of porcine PK‐15 cells produced rapid cytopathic effects (CPEs), including shrinking, rounding and detaching, and peak titre of 109.3 TCID50/ml occurred at 24 hr post‐infection. Electron microscopy and ultra‐thin sectioning revealed spherical GETV particles of 70 nm diameter with an isometric interior and are found to be lining the outer membrane of infected cells. Whole‐genome analysis showed that the two GETV isolates are identical to each other and cluster with Group III strains of GETV, sharing 96.1%–99.7% nucleotide sequence identity with all available reference strains. The most closely relative of the obtained GETV isolates was porcine strain HNJZ‐S2 from Henan province (99.7%), with 98.6% sequence identity shared with equine GETV strain GZ201808 first identified in Guangdong province, indicating different sources for porcine and equine GETV infections in this region. No evidence of GETV infection was found in 497 archived porcine samples collected between 1990 and 2018 in Guangdong province.

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