Parvovirus B19 is an infectious member of the parvovirus family, and the only member of this family capable of affecting humans. It causes a rash on the face, especially in children, and is sometimes known as slapped cheek syndrome, erythema infectiosum or fifth disease. Symptoms include a rash over the face, which may extend to the nose and mouth area, as well as on the upper arms and legs. In adults, sufferers may have swelling of the joints and difficulty walking and bending. 

This disease is usually mild and self-resolving, but it can cause serious problems in some people. Pregnant women in the first trimester may suffer from spontaneous miscarriage if they get this disease. People with sickle cell anemia can suffer from a sudden drop in hemoglobin. Those with compromised immune systems are often at risk of complications if exposed to Parvovirus B19. 

Testing is appropriate for people who may be at risk of complications or reactions from the disease. These tests may occur in the form of IgM or IgG antibody tests, which detect the first antibodies the body produces and the long-term antibodies, respectively. In some cases, viral detection may be appropriate. This technique detects active parvovirus in people with anemia or immune problems, since they may not produce normal levels of antibodies. Reticulocyte tests may sometimes be performed along with a parvovirus test to evaluate production of red blood cells.