Fathoming Fifth Disease

Fifth disease is a mild viral illness that is common in children. It is caused by infection with the human parvovirus B19. The name fifth disease reflects the historical belief that it was one of the five diseases that produced a rash in children.

Fifth disease is also called erythema infectiosum. Erythema (redness) refers to the characteristic "slapped cheek" red rash on the face. This rash may itch. There may also be a lacy red rash on the trunk, arms, and legs. Before there is any rash, the child may have a low-grade fever and symptoms of a cold for several days. The rash itself goes away in seven to 10 days.

The causative virus, parvovirus B19, is thought to be transmitted from person to person via secretions from the mouth or nose. Sharing contaminated drinking cups or toothbrushes may transmit the virus. Unlike some other illnesses with rash, the contagious period in fifth disease is the time before the rash appears, when the child appears to just have a cold or a mild, nonspecific illness.

Fifth disease is very contagious. The CDC (U.S. Centers for Disease Control and Prevention) states that during an outbreak of fifth disease in a school, up to 60% of exposed children can contract the disease.

Frequent hand washing may help prevent spread of the disease. Isolating someone with the rash of fifth disease is not an effective preventive measure, since the contagious period has already passed by the time the rash appears.

Fifth disease in adults

About half of all adults already have antibodies to parvovirus B19, indicating a prior infection. Those who did not have fifth disease as children can contract it as adults. Aside from the typical rash seen in children, adults may develop aches, pain, redness, and swelling of the joints. This form of arthritis most commonly involves the knees, fingers, and wrists.

Not everyone who becomes infected with parvovirus B19 becomes ill. About 20% of those infected do not have any signs or symptoms. Others may experience only mild, nonspecific symptoms without the characteristic rash of fifth disease.

In most people, fifth disease is not a serious illness. Since this is a viral illness, antibiotics are not effective. Usually, no treatment is necessary, although your doctor may suggest over-the-counter medications for the itching or fever.

However, in people with chronic anemia such as from sickle cell disease, parvovirus infection can cause severe acute anemia that requires immediate medical treatment. People with immune deficiency -- from leukemia, cancer, HIV, inherited immunodeficiency or immunosuppressive drugs -- are also at risk for severe illness from parvovirus B19.

In some pregnant women, infection with parvovirus B19 can lead to severe anemia in the unborn baby and sometimes a miscarriage. This occurs in less 5% of pregnant women who become infected and is most common in the first half of pregnancy. There is no evidence that parvovirus B19 can cause birth defects or mental retardation.