Emergence of novel porcine reproductive and respiratory syndrome viruses (ORF5 RFLP 1-7-4 viruses) in China.

Porcine reproductive and respiratory syndrome viruses (PRRSVs) pose a serious threat to the porcine industry of China, and the importation of novel strain(s) makes it challenging to control these viruses. Several NADC30-like PRRSV outbreaks have occurred in mainland China since 2013. In the current study, we report two novel PRRSVs, designated LNWK96 and LNWK130, which belong to lineage 1 and are closely related to US strains with ORF5 restriction fragment length polymorphism (RFLP) 1-7-4. The two viruses had a 100-aa deletion in the nsp2 gene corresponding to positions 328-427 in the VR-2332 strain, which was consistent with most of the ORF5 RFLP 1-7-4 viruses. Recombination analyses indicated that both viruses derived from the recombination of 1-7-4 isolates and ISU30 or NADC30, which were isolated in the United States. Taken together, these results demonstrate the emergence of ORF5 RFLP 1-7-4-like (NADC34-like) PRRSVs in China for the first time.