Evolutionary analysis of Tembusu virus: evidence for the emergence of a dominant genotype.

We recently identified Tembusu virus (TMUV) as a causative agent of duck infectious disease, which has spread in China since 2010. A recent study has indicated a potential case of human infection by TMUV, highlighting the need for further study of TMUV, especially its evolution. Because no information exists regarding the evolution of TMUV, we conducted comprehensive phylogenetic analyses using the largest collection of complete open reading frame (ORF) sequences of TMUV. Our results indicated that two lineages of viruses were associated with the 2010 outbreak in China, and lineage II, in particular sublineage II-c, has arisen as the dominant lineage currently circulating. We inferred that the most recent common ancestor (MRCA) of this TMUV was emerged around 1996. Evidence of natural recombination was also detected in TMUV. Molecular adaptation analyses revealed that strong negative selection shaped the evolution of TMUV, while a number of codons subjected to positive pressure were also identified. Our study, for the first time, illustrated the evolutionary history and character of TMUV and will be helpful for vaccine and diagnostic development.