In 2006, an emerging highly pathogenic strain of porcine reproductive and respiratory syndrome virus (PRRSV), which causes continuous high fever and a high proportion of deaths in vaccinated pigs of all ages, broke out in mainland China and spread rapidly to neighboring countries. To examine the epidemiology and evolutionary characteristics of Chinese PRRSV after the 2006 outbreak, we tested 2,981 clinical samples collected from 2006 to 2010 in China, determined 153 Nsp2 sequences and 249 ORF5 sequences, and analyzed the epidemiology and genetic diversity of Chinese PRRSV. Our results showed that the percentage of PRRSV-positive specimens collected from sick pigs averaged 60.85% in the past 5 years and that the highly pathogenic PRRSV has become the dominant strain in China. Furthermore, a reemerging strain which apparently evolved from the highly pathogenic PRRSV strain in 2006 appeared to be widely prevalent in China from 2009 onwards. Sequence analyses revealed that the hypervariable region of Nsp2 in most of the isolates contained a discontinuous deletion equivalent to 30 amino acids, along with other types of deletions. Extensive amino acid substitutions in the GP5 sequence translated from ORF5 were found, particularly in the potential neutralization epitope and the N-glycosylation sites. Our results suggest that Chinese PRRSV has undergone rapid evolution and can circumvent immune responses induced by currently used vaccines. Information from this study will help in understanding the evolutionary characteristics of Chinese PRRSV and assist ongoing efforts to develop and use PRRSV vaccines in the future.

Here we report, for the first time, the nearly full-length genome sequence of porcine bocavirus (PBoV), a recently discovered parvovirus from pigs. Phylogenetic trees based on this genome sequence showed that PBoV belongs to the branch containing the genus Bocavirus, which comprises canine minute virus (CnMV), bovine parvovirus, gorilla bocavirus and human bocavirus (HBoV), and was most closely related to the group containing CnMV. PBoV was predicted to contain three potential ORFs encoding the non-structural protein NS1, the characteristic NP1 protein and the capsid protein VP1/VP2, with an organization similar to that of known bocaviruses. Interestingly, the NS1 gene of PBoV was more similar in length to the homogeneous gene found in HBoV than to those of other known bocaviruses. In addition, highly conserved unique splice-donor and -acceptor sites were identified in the NS1 gene of HBoV and PBoV.