Parvovirus B19 (B19) is an erythrovirus and recent studies have classified B19 as a genotype 1 erythrovirus with genotypes 2 (erythrovirus K71 or A6) and 3 (erythrovirus V9) also present in the human population. B19 is a significant human pathogen which can cause foetal hydrops and foetal death if material infection, followed by transplacental foetal infection, occurs during pregnancy. The virus is also transmitted by inter-personal contact and potentially via blood product adminstration. Symptoms of B19 infection include malaise, rash and anthralgia. Significantly, maternal B19 infection during pregnancy can be asymptomatic and so careful monitoring of at-risk pregnancies is recommended. Both antibody- and cell-mediated immunity play an important role in the anti-viral response and effective diagnostic test systems, for both B19 antibody and DNA detection, are now available. B19-induced foetal hydrops can be effectively treated by intrauterine blood transfusion: however, no vaccine is available to prevent infection at present.