Chikungunya virus. Coloured transmission electron micrograph (TEM) of chikungunya viruses (brown) infecting a cell. This alphavirus is composed of an RNA (ribonucleic acid) genome enclosed in a protein coat, or nucleocapsid, which is itself surrounded by a lipoprotein envelope. The virus, which is transmitted by mosquitoes, causes a rare form of viral fever. Symptoms include a high fever, rash and arthritic joint pain. Magnification: x162,000 when printed at 10 centimetres tall.