Conclusion
In summary, multiple subtypes of PRRSV commonly coexist on single pig farms. NADC34-like PRRSV, which correlated with the death curve, was first reported to be one of the main endemic strains on a pig farm in Heilongjiang Province, China. NADC34-like PRRSV from this farm had high nucleotide similarity and a 100-aa deletion in the NSP2 protein but no recombination. The genetic diversity of NADC34-like PRRSV is relatively singular, but it has a relatively high evolution rate. The prevalence of NADC34-like PRRSV on other pig farms in China needs further attention.