The B19 virus, referred to as parvovirus B19, was first known human virus in the family of parvovirus. It causes a childhood rash called fifth disease or commonly called slapped cheek syndrome. Discovered in 1975 by Yvonne Cossart, the virus gained its name because it was found in well B19 of a large series of Petri dishes.
The virus is mainly spread through infected respiratory droplets. Symptoms usually appear six days after exposure and last about a week. Patients aren’t usually contagious after symptoms show but before that they can be infectious. A large increase in the number of cases is seen every three to four years.
It only infects humans and there is no vaccine available. Fifth disease is only one of several expressions of Parvovirus B19. It is most common in children aged six to ten years.
Patients usually develop illness after an incubation period of four to fourteen days. It usually commences with fever and malaise while the virus is most abundant in the bloodstream, and patients are usually no longer infectious once the rash stage happens. The rash is typically described as “slapped cheeks,” with erythema across the cheeks, forehead, and mouth. These rashes can last for up to 5 weeks.
B19 is also a cause of chronic anemia in people who have AIDS. In adults B19 can lead to a seronegative arthritis which is treated with analgesics. Women are twice as likely as men to contract arthritis after parvovirus infection. Up to 15% of all new cases of arthritis can be contributed to parvovirus although this form of arthritis doesn’t progress to other forms of arthritis. Symptoms usually last 1 to 3 weeks although it can last longer.
It is dangerous in sickle cell anemia patients because parvovirus infection can cause an arrest in red blood cell production. If infection happens in one of these patients it is called an aplastic crisis and is usually treated with a blood transfusion.
Infection in pregnant women can cause hydrops fetalis due to severe fetal anemia. Fetal loss risk is about 10% if infection occurs before pregnancy week 20.