Simian virus 40 particle. Computer artwork of the capsid of simian virus 40 (SV40) with proteins represented by coloured blobs. The capsid is a protein coat that encloses the virus's DNA (deoxyribonucleic acid) genome. This capsid is icosahedral in shape, with 20 triangular faces. The virus infects both monkeys and humans, although it is unclear whether infection causes symptoms in humans. In monkeys with suppressed immune systems, the virus causes kidney disease and can damage the myelin sheaths surrounding nerve fibres.