The widely used pseudorabies virus (PRV) Bartha-K61 vaccine has played a key role in the eradication of PRV. Since late 2011, however, a disease characterized by neurologic symptoms and a high number of deaths among newborn piglets has occurred among Bartha-K61–vaccinated pigs on many farms in China. Clinical samples from pigs on 15 farms in 6 provinces were examined. The PRV gE gene was detectable by PCR in all samples, and sequence analysis of the gE gene showed that all isolates belonged to a relatively independent cluster and contained 2 amino acid insertions. A PRV (named HeN1) was isolated and caused transitional fever in pigs. In protection assays, Bartha-K61 vaccine provided 100% protection against lethal challenge with SC (a classical PRV) but only 50% protection against 4 challenges with strain HeN1. The findings suggest that Bartha-K61 vaccine does not provide effective protection against PRV HeN1 infection.

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cIn China, a majority of the highly pathogenic porcine reproductive and respiratory syndrome (HP-PRRSV) strains were seeded by the 2006 outbreak. However, the most recently emerged (2013-2014) HP-PRRSV strain has a very different genetic background. It is a NADC30-like PRRSV strain recently introduced from North America that has undergone genetic exchange with the classic HP-PRRSV strains in China. Subsequent isolation and characterization of this variant suggest high pathogenicity, so it merits special attention in control and vaccine strategies. P orcine reproductive and respiratory syndrome (PRRS) is characterized by respiratory distress in nursery swine and reproductive failure in sows and has resulted in huge economic losses to the global swine industry since its first recognition in the United States in 1987 (1). In China, highly pathogenic PRRSV (HP-PRRSV) has been circulating and predominating in the field since the initial outbreak in 2006 and has resulted in the loss of more than one million pigs (2-5). Retrospective studies of that outbreak have shown that the highly pathogenic variant emerged from less pathogenic PRRSV strains in China (6), which were initially introduced from North America in the 1990s. CH-1a was the earliest representative of this group (7). Following the outbreak, more-stringent biosecurity controls and a targeted immunization campaign were undertaken to limit HP-PRRS in China.However, despite these measures, HP-PRRSV has experienced recurrent population expansions since the initial outbreak. One such reemergence was associated with genetic exchange between two HP-PRRSV viruses circulating in the field (8). Another recent outbreak (2013)(2014) is probably in the early stage of emergence. It has occurred in several provinces of China and is characterized by high fever, cough, anorexia, red discoloration of the body, and blue ears. Diseased pigs also have multiple visceral lesions. Their lungs display consolidation, and their lymph nodes are enlarged and hemorrhagic. The rates of morbidity and mortality due to this new HP-PRRSV are very high. An affected farm in Jilin Province had a morbidity rate of 100% and a mortality rate of 76.6% (230/ 300).We obtained the representative open reading frame 5 (ORF5) sequences from two farms that experienced the disease, i.e., JL580 and HLJ58 from Jilin Province and Heilongjiang Province, respectively. Phylogenetic analyses using the PhyML version 3.0 software (9) suggested that these viruses are distantly related to the classic HP-PRRSV strains in China, which belong to lineage 8 (Fig. 1A). Instead, they nested deeply within diverse lineage 1, which originated in Canada and is now prevalent in both the United States and Canada (10). Interestingly, the virus is also closely related to a group represented by NADC30, a moderately virulent strain isolated in 2008 in the United States (11). Furthermore, the phylogenetic topology of the diversity surrounding this new HP-PRRSV suggests, with high resolution, a transmission chain from Canada to the Unit...