A child with Fifth Disease caused by parvovirus, courtesy Andrew Kerr via Wikipedia
Parvovirus B19, now more properly called erythrovirus, is the only one of a group of related viruses that cause symptoms in humans. Although symptoms are usually mild and resolve themselves quickly, parvovirus can cause serious complications, particularly in the immunocompromised and pregnant women. It is very contagious. A person living with a person with the virus has about a 50% chance of being infected. A person in the same classroom has about a 25%. It is spread by respiratory droplets. The disease has been a frequent differential diagnosis.
An individual will be contagious as soon as they are exposed to the disease, but will not show any symptoms for, in most cases, at least two weeks. However, symptoms generally resolve without treatment in about one further week.
The most usual presentatiion of the virus is Fifth Disease, which causes spotting on the body that resembles the flushing caused by slapping. Another common presentation, particularly in adults, is joint pain that usually responds to analgesics.
The presence of the virus usually leads to the body ceasing to produce red blood cells. In an otherwise healthy patient, this is usually not a concern. However, in immunocompromised patients, the virus can lead to chronic anemia. Treatment with erythropoetin and immunoglobulin can be helpful in such cases. In patients with a history of a red blood cell disease, such as sickle cell anemia, the red blood cell count can crash, requiring a transfusion.
In a pregnant woman in the first five months of pregnancy, the virus can cause hydrops fetalis, which can lead to miscarriage or stillbirth.