Synopsis
Parvovirus B19 is a nonenveloped, single-stranded DNA virus that targets erythroid progenitor cells, inhibiting erythropoiesis and causing varied clinical manifestations. Parvovirus B19 infection occurs worldwide and is commonly seen during the late winter to early summer. Three genotypes (genotypes 1, 2, and 3) have been identified and vary in geographic distribution. Genotype 1 is the most common and is found worldwide. Genotype 2 is restricted to the United States and Europe. Genotype 3 is found in sub-Saharan Africa and South America.
Parvovirus B19 is most often transmitted via respiratory droplets; however, vertical transmission and hematogenous transmission may occur. Infection can occur throughout life. Approximately half of individuals are seropositive by 15 years of age, while over 70% of adults have measurable parvovirus B19-specific IgG antibodies.
Clinical manifestations and severity of disease depend on host characteristics, including age, sex, and general health prior to infection. Most individuals are either asymptomatic or experience nonspecific, flu-like symptoms. Approximately 25% will experience clinical conditions associated with parvovirus B19 infection, including erythema infectiosum, arthropathy, transient aplastic crisis, chronic red cell aplasia, and/or fetal death. Individuals most at risk for development of serious complications include patients with underlying hematologic disease, immunosuppressed patients, and pregnant patients (infection during pregnancy may rarely lead to fetal death).
Look For:
There are currently 5 well-established clinical conditions associated with parvovirus B19 infection:
- Erythema infectiosum (Fifth disease) – Erythema infectiosum is the most common clinical manifestation of parvovirus B19 infection and most commonly occurs in school-aged children. Nonspecific prodromal symptoms occur following initial infection and correspond with parvoviremia. The development of a characteristic erythematous malar rash (slapped-cheek rash) typically occurs 2 weeks post-infection and is associated with the development of parvovirus B19-specific antibodies. A reticulated rash on the trunk and/or limbs may also develop. Recurrence of rash following resolution of infection is not uncommon and can be triggered by a variety of stimuli including sunlight, stress, or exercise.
- Arthropathy – Arthropathy is a common manifestation of parvovirus B19 infection among adults and also occurs in approximately 5% of infected children. Clinical manifestations among adults and children differ. Parvovirus B19-associated arthropathy in adults typically includes symmetric involvement of the small joints of the hands, wrists, knees, and feet. While most arthropathy resolves in <6 weeks, a small proportion of adults have persistent or recurring symptoms lasting >6 months. Even among individuals who develop chronic arthropathy, joint destruction does not occur. Approximately 50% of adults also develop a faint, mildly itchy rash that accompanies the arthropathy. The development of this rash is less common and less pronounced in adults than in children. Arthropathy in children tends to be asymmetric and typically involves only the knees.
- Transient aplastic crisis – Transient aplastic crisis (TAC) can occur following parvovirus B19 infection among individuals with pre-existing hematologic abnormalities that lead to decreased erythrocyte counts, including sickle cell anemia, hereditary spherocytosis, and iron deficiency anemia. Transient aplastic crisis occurs when, following parvovirus B19 infection in susceptible individuals, erythropoiesis is temporarily halted and severe anemia ensues. The onset of TAC corresponds to parvoviremia and typically resolves within 2 weeks following parvovirus B19-specific antibody development and clearance of the infection, at which time red blood cell production returns to baseline. In a small proportion of individuals, TAC may lead to dramatic declines in hemoglobin that cause / exacerbate congestive heart failure, cerebrovascular events, or acute splenic sequestration. See aplastic anemia.
- Chronic red blood cell aplasia – Chronic red blood cell aplasia is most common among immunocompromised individuals (eg, individuals with HIV infection, cancer, or congenital immunodeficiencies or organ transplant recipients) with persistent parvovirus B19 infection due to their inability to mount an effective immune response. Patients may present with symptoms associated with severe anemia such as fatigue and pallor. Rash and arthropathy are not commonly seen due to their association with deposition of immune complexes. See pure red cell aplasia.
- Nonimmune hydrops fetalis / miscarriage / intrauterine death – Vertical transmission of parvovirus B19 infection from mother to child may lead to hydrops fetalis, miscarriage, or intrauterine death. Hydrops fetalis results from severe anemia and is associated with fetal edema and a thick, hydropic placenta. Risk for both hydrops fetalis and intrauterine fetal death varies with timing of maternal infection. Risk for hydrops fetalis is highest when infection occurs between 9 and 20 weeks; fetal death most often occurs from infection between 20 and 24 weeks gestation.
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