Individuals with erythema infectiosum have a fever and a rubelliform rash that begins on the face and spreads to the trunk and limbs. In patients with a preexisting hemolytic anemia (e.g., sickle cell anemia), the disease can cause aplastic crisis (transient bone marrow erythroid aplasia). In women, disease late in pregnancy can cause spontaneous abortion and edematous anemic stillbirth (hydrops fetalis).
Structure
Parvoviruses are non-enveloped, icosahedral particles 18 to 26 nm in diameter. Plus and minus DNA strands are packaged into separate virions in approximately equal proportion. There are two capsid proteins.
Classification and Antigenic Types
Parvoviruses are classified by size, morphology, and genomic organization. A single antigenic type is associated with human disease.
Multiplication
Replication takes place in the nucleus of dividing cells. The single-stranded DNA genome forms an intermediate double-stranded form, which replicates to form progeny-positive and -negative single-stranded DNA. Positive and negative strands are packaged separately in viral capsids in equal numbers.
Pathogenesis
The disease is transmitted by the respiratory route. The virus replicates in committed erythroid precursor cells in the bone marrow, leading to erythroid aplasia. Aplastic anemia develops in patients with underlying hemolytic anemia, and rash and arthralgia develop at the time specific antibody appears.
Host Defenses
Specific IgM and IgG antibodies develop in response to infection.
Epidemiology
Erythema infectiosum is found worldwide. Outbreaks occur predominantly in spring, mainly in school children and young adults, with peaks of activity at 4- to 5-year intervals.
Diagnosis
Diagnosis is by detecting viral DNA in serum and a rise in parvovirus-specific IgM or IgG.
Control
No specific antiviral therapy or vaccine is yet available.
