Fifth disease is an infectious disease caused by Parvovirus B19 that is usually seen in children. It is slightly more common in girls than in boys. 70% of cases are children aged 5–15.
Fifth Disease, a rash illness most common in children aged 5–15, occurs mostly in the spring months. Fifth Disease begins with fever, a runny nose and headache, and a few days after these symptoms a redness resembling a "slapped cheek" appears on the face.
The disease often passes without symptoms or is confused with measles. In adults, especially women, pain and swelling may occur in the joints of the hands and feet or in the knees. In some adults these symptoms may occur without a rash, and the joint pain may last 1–3 weeks.
The incubation period is 7–10 days. About a week after contact, mild prodromal symptoms (headache, fever, sore throat, itching, runny nose, abdominal pain, arthralgia) appear and disappear within 2–3 days. Joint pain can be seen in up to 50% of adults. After a symptom-free period of about 7 days, the typical exanthem (rash) appears, which has 3 stages. First, a red erythema on the face described as a "slapped cheek appearance", with perioral pallor, appears. Usually 1–4 days later, a lace-like maculopapular rash develops on the trunk and proximal limbs. In the third stage, the rash that has faded may recur weeks or months later in response to triggers such as exercise, irritation, bathing or warming from sunlight. The rash is itchy, especially in adults. There is no enanthem. The rash is seen in 75% of children and in less than 50% of adults.
Fifth Disease can be transmitted through respiratory secretions such as saliva, phlegm and nasal discharge when sneezing or coughing. The disease is contagious during the period before the rash appears, which looks like a "common cold". Fifth Disease is also a risk for people with leukaemia, other cancer patients, transplant recipients and those with immunodeficiency. After having fifth disease, permanent immunity is usually acquired. The rash may increase with hot baths, sun and rising ambient temperature, and may decrease in cool environments; for this reason the patient should stay away from hot environments and shower with cool water.
Complications
Arthropathy (in the form of symmetrical polyarthritis, usually affecting the fingers, developing 2–3 weeks after contact and seen mostly in adult women), aplastic crises in patients with chronic haemolytic anaemia, and hydrops fetalis (in 10% of babies of mothers who have the disease in early pregnancy) may occur.
Epidemiology and transmission
Although transmission is usually through respiratory secretions, transmission through waste and parenteral transmission via blood transfusion or vertical transmission from mother to baby have also been reported. It is seen mostly in the winter and spring months and causes cyclical epidemics every 4–7 years. The chance of transmission through household contact is 30–50%.
Diagnosis
Because the rash is typical and the prognosis of the disease is good, routine laboratory testing is not required. The white blood cell count is usually normal; mild eosinophilia may be seen. Serological diagnosis may be needed if haemolytic anaemia, pregnancy or arthropathy is also present. IgM positivity in the acute phase, or at least a 4-fold rise in IgG in convalescent serum compared with the acute phase, or seroconversion from negative to positive, confirms the diagnosis. The virus cannot be grown in standard cell cultures. PCR and antigen tests are also available.
Differential diagnosis
Measles, rubella, roseola infantum, scarlet fever, rickettsial and enteroviral rashes, systemic lupus erythematosus, drug eruptions, allergic rashes.
Treatment
There is no specific treatment. Symptomatic treatment (antipyretics, antihistamines…) can be given. It is advisable to keep patients away from excessive heat and sunlight.
Prevention
Once the rash appears, the person is no longer contagious. Patients with aplastic crises remain viraemic until their red blood cell count returns to normal and can transmit the virus. It is advisable to keep these patients away from pregnant women and from patients with chronic haemolytic anaemia or immunodeficiency.