Erythema infectiosum (fifth disease) is an exanthematous viral infection caused by the human parvovirus B19. It affects most often children aged 5-15 years and occurs as minor epidemics in the spring.
In a previously healthy child, the disease is usually mild and the child recovers without problems.
Lack of tenderness, symmetry, and good general condition differentiate the disease from bacterial cellulitis.
A maculopapular rash follows the cheek lesions within 1-4 days. The rash starts from the extensor surfaces of the upper limbs and spreads in a reticular pattern predominantly on the limbs.
The rash lasts typically 3-7 days, but it can disappear and reappear over several weeks.
A part of the patients have fever, headache, pharyngitis and myalgia before the rash appears.
During the rash, 15-30% have fever. Arthralgia and arthritis are rare in children, but more common in adults.
Incubation time is 6-16 days. School-aged children are mostly affected, and several members of the same family may fall ill. In the rash-phase the disease is not anymore infectious, and children can attend day care of school, and isolation does not provide any benefit, e.g., in protecting pregnant women.
Up to one half of the infections are subclinical.
Erythema infectiosum strikes the patient only once.
The virus may cause aplastic crisis in a patient with malignant haematological disease. In association with an aplastic crisis the patient is infective for at least one week from the onset of symptoms.
Diagnosis and treatment
The diagnosis is based on the clinical picture.
Serological diagnosis (a 4-fold increase in the IgG concentration in paired serum samples or positive IgM) is available, but usually not necessary in practice.
The virus may be demonstrated in synovial fluid or in bone marrow using PCR technique.
The treatment is symptomatic.
Infection during pregnancy
Of pregnant women, typically 50-60% have already had the disease before pregnancy. The risk of a seronegative woman to catch the infection during pregnancy is a few per cents, during epidemics somewhat greater. A fresh infection in a pregnant woman is transmitted to the foetus in 30-50% of the cases.
The virus has not been found to cause malformations. It may, however, cause foetal anaemia especially in early pregnancy. An intrauterine infection before the 20th week of pregnancy leads to foetal death in about 10% of the cases; later in pregnancy the risk decreases to about 1%.
If a pregnant woman is exposed to erythema infectiosum (e.g. a contact with a person with confirmed disease, before the appearance of the rash), determine the antibody concentrations http://www.dynamed.com/condition/congenital-parvovirus-b19-infection#BLOOD_TESTS. If the exposure is continuous, e.g. at work with children in a day-care centre during an epidemic, the antibody concentrations in a seronegative pregnant woman should be monitored every 2 to 3 weeks until the epidemic is over. For the period of these examinations the woman should be relocated to another place of work or away from work. If a fresh infection is detected, refer the patient to a prenatal clinic for follow-up http://www.dynamed.com/condition/congenital-parvovirus-b19-infection#IMAGING_STUDIES in order to diagnose foetal disease and to discover signs of possible foetal anaemia. If the mother has already established immunity, she may continue working. In a seronegative mother a transfer to another work location may be considered for the period of the epidemic.
References
American Academy of Pediatrics. Parvovirus B19. In: Pickering LK, Baker CJ, Kimberlin DW, Long SS, eds. Red Book: 2015 Report of the Committee on Infectious Diseases. 30th ed. Elk Grove Village, IL: American Academy of Pediatrics; 2015:593-596.
Koch WC, Harger JH, Barnstein B, Adler SP. Serologic and virologic evidence for frequent intrauterine transmission of human parvovirus B19 with a primary maternal infection during pregnancy. Pediatr Infect Dis J 1998 Jun;17(6):489-94. [PubMed]