Fifth disease is often diagnosed by the clinical signs and symptoms, most commonly the slapped cheek appearance due to the facial rash, and acute polyarthropathy, especially in adults. If necessary, laboratory testing is performed to distinguish recent from past infection, as well as to test the immune status.
Testing for B19 antibodies is not routinely done. However, it is often carried out if a pregnant woman is exposed to the virus and is suspected to have the fifth disease. During pregnancy, the fetus is especially at risk because of its immature immune system and the infection of hemopoietic tissues, such as the liver, leading to severe anemia and congestive heart failure. This typically results in hydrops fetalis, intrauterine fetal death or sometimes congenital anemia.
Asymptomatic infection is quite common in both adults and children, as high as 25 %. Even among women with IgM positivity, less than 50% remembered any history of a rash or joint pain.
In some patients, the symptoms closely resemble those of the common influenza virus.
In patients who have a hemolytic disorder, or are immunocompromised, infection with parvovirus B19 causes not only erythema infectiosum but also transient aplastic crisis and pure red cell aplasia. Patients with hemolytic anemia who develop an aplastic crisis can fail to develop symptoms if B19 infection follows a recent blood transfusion, as the red cells from the donor have a longer lifespan than the host’s own red cells, and thus they mask the deficiency in bone marrow red cell production.
The diagnosis is based upon the clinical features as well as the detection of specific IgM antibodies using an ELISA (enzyme-linked immunosorbent assay) or through viral DNA detection using PCR techniques or dot-blot hybridization.
Specific B19 IgM detection is the technique of choice for the diagnosis of infection in healthy individuals. These assays can be depended upon to detect present or recent infection in individuals who have a normal immune function. These antibodies can be detected for the next 2-3 months. Indirect detection methods are not preferred as they are less sensitive and have low specificity. IgG antibodies are equally well detected by both direct and indirect assays. The IgG antibody appears after the second week of infection and persists throughout life.
DNA detection methods are adopted in immunocompromised patients or in those with hemolytic disorders. Hybridization has the advantages of allowing virus quantification and detecting all known virus variants. PCR is, however, far more sensitive and thus achieves lower detection limits, but is easily contaminated. These are reserved for unusual presentations, such as the transient aplastic crisis in hematologic conditions, or chronic infection in immunosuppressed individuals.
NS1 IgG may indicate persistent B19 infection but is, in any case, detected only in very late infection, after six weeks.
In most healthy individuals, no treatment is required other than symptomatic, for the itching, fever or joint pain, as with anti-inflammatory drugs. If complications develop, a medical consultation is necessary.
If the infection is confirmed during pregnancy, and the woman has no previous immunity, weekly ultrasounds are mandatory to detect hydrops fetalis, while cordocentesis and intrauterine transfusions are required for prevention of intrauterine death.
In patients with persistent infection or red cell complications, immunoglobulin therapy is the most effective as it reduces the viral load in the blood and produces a rapid and significant improvement in anemia. Patients with anemia may benefit from blood transfusions or stem cell therapy in some cases. Chemotherapy or steroid treatment may have to be stopped for a while to allow the immunity to improve.
Erythema infectiosum is a mild disease self-limited. Children with the infection need not stay away from school as the infectivity dies down once the rash appears. However, to prevent respiratory droplet spread, hand washing at frequent intervals is recommended. In addition, all individuals in such a setting should be reminded to cover their nose and mouth when coughing or sneezing and to avoid touching these organs, as well as the eyes.
In pregnancy, the decision to keep away from an occupational location where an outbreak is occurring should be taken by the pregnant woman in consultation with her family, health care provider, and employer.
Vaccination is both effective and feasible but commercial development is slow due to the lack of ready market demand.