Parvovirus B19 is a small DNA virus which was discovered by chance in 1975.
The virus is spread by infected respiratory droplets and the illness usually starts after an incubation period of between four and fourteen days. Patients are usually no longer infectious once the characteristic rash of this disease has appeared. Any age may be affected although it is most common in children aged six to ten years. By the time adulthood is reached about half the population will have become immune following infection at some time in their past. Outbreaks can arise especially in nurseries and schools.
A significant increase in the number of cases is seen every three to four years; the last epidemic year was 1998. Parvovirus is also known as "fifth disease" because it was the fifth cause of a superficial red rash of childhood to be identified. Other similar rashes include measles, rubella [German measles] and scarlet fever. Parvovirus B19 only causes an infection in humans; cat and dog parvoviruses do not infect humans.
Parvovirus B19 infection is usually mild, but it does have the ability to cause some serious problems: it is associated with spontaneous abortion in pregnant women, and with aplastic crisis in persons with chronic hemolytic anemia.
