Parvovirus B19 is the only representative of its species currently known to medicine to have an unequivocally negative effect on the human body. It can cause arthritis, glove or sock syndrome, as well as haematological problems. It is particularly dangerous for pregnant women, as transmission from mother to foetus is possible in up to 33% of cases, and the infected foetus may show symptoms of generalised swelling, congenital malformations or even die.