DESCRIPTION

Parvoviruses are small, single-stranded DNA viruses. A type of parvovirus designated B19 infects humans. (Animal parvoviruses are responsible for commonly occurring blood disorders in cats and dogs.) An acute viral disease characterized by mild symptoms and a blotchy rash beginning on the cheeks and spreading to the extremities. Primary infection in young children can cause an illness known as erythema infectiosum, “slapped cheek” or fifth disease. Congenital infection can damage the baby's blood forming capacity causing severe anemia and edema similar to that seen with Rh incompatibility and known as Hydrops fetalis. Human Parvovirus B19 can also cause anemia in adults, especially in those with an underlying hematologic disorder or with HIV infection.

METHOD OF TRANSMISSION

Fifth disease is caused by the human parvovirus B19 agent. It occurs most often during the spring with localized outbreaks in preschoolers or school-age children and adolescents. Parvovirus B19 has been found in the respiratory secretions of infected persons before the onset of rash, when they appear to "just have a cold." Respiratory secretions (e.g., saliva, sputum, or nasal mucus) spread it and the incubation period is to 12 days. The duration of the illness is usually five days. However, the rash may recur for several weeks and may be brought on by exposure to sunlight, heat, exercise, fever, or emotional stress.

The virus is probably spread from person to person by direct contact with the secretions, such as sharing drinking cups or utensils. In a household as many as 50% of susceptible persons exposed to a family member who has fifth disease may become infected. During school outbreaks, 10% to 60% of students may get fifth disease.

Fifth disease is caused by infection with human parvovirus B19. This virus infects only humans. Pet dogs or cats may be immunized against "parvovirus," but these are animal parvoviruses that do not infect humans. Therefore, a child cannot "catch" parvovirus from a pet dog or cat, and a pet cat or dog cannot catch human parvovirus B19 from an ill child.

SYMPTOMS/CLINICAL CONDITIONS

Fifth disease is a mild rash illness that occurs most commonly in children. Erythema infectiosum usually begins with bright red cheeks producing a "slapped-cheek" appearance. Following this, a rash appears on the extremities and trunk. The rash fades centrally giving a lacy (reticulated) appearance to the rash. The rash fades over a period of one to two weeks. This illness is seldom associated with fever, however, an ill child may have a low-grade fever, malaise, or a "cold" a few days before the rash breaks out and joint pain, also called arthralgia (mild). The child is usually not very ill, and the rash resolves in 7 to 10 days.

An adult who is not immune can be infected with parvovirus B19 and either have no symptoms or develop the typical rash of fifth disease, joint pain or swelling, or both. Usually, joints on both sides of the body are affected. The joints most frequently affected are the hands, wrists, and knees. The joint pain and swelling usually resolve in a week or two, but they may last several months. About 50% of adults, however, have been previously infected with parvovirus B19, have developed immunity to the virus, and cannot get fifth disease.

The incidence of parvovirus B19 infection is unknown but studies suggest that 40 percent to 50 percent of adults have antibodies to the virus; this indicates a high degree of infection and also suggests that many infections go unnoticed.

METHODS OF DIAGNOSIS

The patient is examined for the appearance and pattern of the rash. The appearance of the rash usually makes the diagnosis straightforward. Antibody titer studies for parvovirus B19 are available although rarely performed. They can be obtained through the Centers for Disease Control and some state health departments. Viral titers for parvovirus B19 are usually obtained when trying to diagnose 'transient aplastic crisis' and persistent anemias, occasional manifestations of parvovirus B19 infection in individuals with sickle cell anemia, hemolytic anemias, HIV infection and other types of immunodeficiency. Virus studies may also be obtained when there is a question of exposure in a pregnant mother whose immune status is not known.

TREATMENT /PROTOCOL

A person infected with parvovirus B19 is contagious during the early part of the illness, before the rash appears. By the time a child has the characteristic "slapped cheek" rash of fifth disease, for example, he or she is probably no longer contagious and may return to school or childcare center. This contagious period is different than that for many other rash illnesses, such as measles, for which the child is contagious while he or she has the rash.

No treatment is usually required for fifth disease in children. Treatment of symptoms such as fever, pain, or itching is usually all that is needed for fifth disease. Adults with joint pain and swelling may need to rest, restrict their activities, and take medicines such as aspirin or ibuprofen to relieve symptoms. The few people who have severe anemia caused by parvovirus B19 infection may need to be hospitalized and receive blood transfusions. Persons with immune problems may need special medical care, including treatment with immune globulin (antibodies), to help their bodies get rid of the infection.

PREVENTION

This is a contagious viral disorder. At this time, there is no vaccine or other proven prevention. Frequent hand washing is recommended as a practical and probably effective method to decrease the chance of becoming infected. Excluding persons with fifth disease from work, child care centers, or schools is not likely to prevent the spread of the virus, since people are contagious before they develop the rash.

CONDITIONS LINKED TO PAROVIRUS 19

Parvovirus B19 is thought to cause other disease manifestations. In healthy adults it may be responsible for an infectious arthritis (particularly in women). In individuals with AIDS (or other immunocompromised persons) it may produce a profound anemia. This form of anemia is called 'transient aplastic crisis'. People who have leukemia or cancer, who are born with immune deficiencies, who have received an organ transplant, or who have human immunodeficiency virus (HIV) infection are at risk for serious illness due to parvovirus B19 infection. Occasionally, serious complications may develop from parvovirus B19 infection during pregnancy.