Sindbis virus

Sindbis virus (SINV) is a member of the Togaviridae family, in the alphavirus subfamily. The virus was first isolated in 1952 in Cairo, Egypt. The virus is transmitted by mosquitoes (Culex spp.) SINV causes sindbis fever in humans and the symptoms include arthralgia, rash and malaise. Sindbis fever is most common in South and East Africa, Egypt, Israel, Philippines and parts of Australia. Sindbis virus is an 'arbovirus' (arthropod-borne) and is maintained in nature by transmission between vertebrate (bird) hosts and invertebrate (mosquito) vectors. Humans are infected with Sindbis virus when bitten by an infected mosquito. SINV has been linked to Pogosta disease in Finland, Ockelbo disease in Sweden and Karelian fever in Russia. Sindbis viruses are enveloped particles with an icosahedral capsid. Its genome is a single stranded RNA approximately 11.7kb long. It has a 5' cap and 3' polyadenylated tail therefore serves directly as messenger RNA (mRNA) in a host cell. The genome encodes four non-structural proteins at the 5' end and the capsid and two envelope proteins at the 3' end. This is characteristic of all Togaviruses. Replication is cytoplasmic and rapid. The genomic RNA is partially translated at the 5’ end to produce the non-structural proteins which are then involved in genome replication and the production of new genomic RNA and a shorter sub-genomic RNA strand. This sub-genomic strand is translated into the structural proteins. The viruses assemble at the host cell surfaces and acquire their envelope through budding. A non-coding RNA element has been found to be essential for Sindbis virus genome replication.