Phylogeny of Sindbis virus isolates from South Africa

Sindbis virus (SINV), the prototype virus in the genus, Alphavirus, is an arbovirus with an extensive geographical distribution. Birds are the main vertebrate hosts for SINV, while Culex mosquitoes serve as vectors and occasionally transmit the virus to humans, causing a febrile illness with a maculopapular rash and arthritis. Currently, little information exists on the genetic diversity within SINV strains from South Africa. The E2 envelope glycoprotein gene was partially sequenced for a panel of 27 South African and African Sindbis virus isolates derived from a human case and from mosquito pools. A phylogenetic analysis was performed using these sequences, together with 65 partial E2 gene sequences from Sindbis virus isolates from elsewhere in the world. The resulting phylogenetic tree suggested five distinct Sindbis virus genotypes. The South African Sindbis virus isolates were grouped within genotype I, together with isolates from Sweden, Finland, Germany and Norway. The phylogeny of Sindbis virus reflects its geographical distribution and corresponds with the major migratory bird flyways, indicating that birds play a major role in Sindbis virus distribution.