Banna virus, China, 1987-2007

Abstract

Banna viruses (BAVs) have been isolated from pigs, cattle, ticks, mosquitoes, and human encephalitis patients. We isolated and analyzed 20 BAVs newly isolated in China; this finding extends the distribution of BAVs from tropical zone to north temperate climates and demonstrate regional variations in BAV phylogeny and mosquito species possibly involved in BAV transmission.

Figure 1

Location of new Banna viruses (BAVs) isolated in China (red triangles) and previously reported BAV isolation sites (black triangles). Countries reporting isolation of BAV are shaded. The names of the countries that are contiguous with BAV isolation sites are labeled. BAV distribution sites in Indonesia, Vietnam, and part of China are located in tropical zones, which lie predominantly between the Tropic of Cancer and the equator. Most BAV distribution sites in China in the area from the Tropic of Cancer to latitude 45°N belong to the northern temperate zone.

Figure 2

Phylogenetic analysis based on the complete coding sequence of the 12th segment of Banna viruses (BAVs) currently isolated. Phylogenetic analyses were performed by the neighbor-joining method using MEGA version 4 software (www.megasoftware.net). Bootstrap probabilities of each node were calculated with 1,000 replicates. The tree was rooted by using Kadipiro virus and Liaoning virus as the outgroup viruses. Scale bars indicate a genetic distance of 0.1-nt substitutions per site. Isolates obtained in China are in boldface. Viruses were identified by using the nomenclature of virus strain/country/year of isolation/origin.