The B19 virus, or parvovirus, was the first found human virus in the parvovirus family. It causes a childhood rash called fifth disease also commonly called slapped cheek syndrome. Yvonne Cossart discovered it by chance in 1975. It gained its name, B19, due to the labeled Petri dishes it was found in.
The virus is classified as erythrovirus due to its capability to invade red blood cell precursors in the bone marrow. It is primarily spread by infected respiratory droplets. Symptoms usually occur about six days after exposure and last about a week. Generally once an individual has B19 IgG antibodies they are considered immune to recurrent infection. Around 50% of adults are immune due to previous infections. The last outbreak was in 1998 and outbreaks generally occur every three to four years.
The virus infects humans only while cat and dog parvoviruses don’t infect humans. There is a vaccine available for small animals but none for humans. Fifth disease is only one of several expression of Parvovirus B19. Generally children are infected although any age is susceptible. Along with the characteristic rash the body has a fever and malaise while the virus is most abundant in the bloodstream. The rash, however, signifies that the infected person is no longer contagious although that is only the case with children. Teenagers and young adults may still be infectious even with the rash.
The virus can lead to seronegative arthritis in adults which can be controlled with analgesics. Women are approximately twice as likely as men to experience arthritis from the parvovirus infection.
Generally arthritis from the virus does not progress to other forms of arthritis and joint symptoms generally only last 1-3 weeks although it is longer in some patients.
The virus can be very dangerous for patients who have sickle cell anemia due to the arrest in production of red blood cells. Generally they need a blood transfusion in order to treat this.
Parvovirus infection in pregnant women can lead to miscarriage or stillbirth. If the infection occurs before week 20 the risk of fetal loss is 10% although minimal after that.