Human parvovirus B19, discovered in 19751 and first linked with human disease in 1981,2 is a small single stranded DNA virus classified within the family Parvoviridae, and the genus Erythrovirus, having tropism primarily for erythroid precursors. B19 is the only parvovirus which has been clearly linked with disease in humans. It replicates only in human cells and is autonomous, not requiring the presence of a helper virus.

Acute B19 virus infection is classically associated with the childhood rash illness, erythema infectiosum (EI), arthralgia, fetal death, and transient aplastic crisis (TAC) in those with shortened red cell survival. However, it has been assumed that in those with a normal immune system, the virus has a relatively simple pathogenesis and that after the acute phase the virus is cleared by a specific humoral immune response. However, increasingly B19 virus and B19 infection have been reported in association with quite atypical and unpredictable findings based on previous assumptions. For example, persistence of the virus in various tissues after acute infection in apparently normal subjects and the association of B19 infection with various connective tissue and autoimmune diseases. This paper will therefore summarise present knowledge of the virus, its known and potential pathogenetic mechanisms, and its associations with human disease, with an emphasis on rheumatic disease.