ERYTHEMA INFECTIOSUM (B19  INFECTION)

Structure & Property	Transmission	Pathogenesis	Clinical findings	Laboratory diagnosis	Treatment	
Family: parvovirus

Genome: single-strand DNA

Size: 18-26nm

Icosahedral, nonenveloped particles	Transmission by inhalations of infected respiratory secretions.

Peak incidence of infection is in childhood, during early school years – from 5 to 10 years old.	Replicates and is shed in upper respiratory tract.

Targets human erythroid progenitor cells; cause lysis leading to anemia.	20% of those infected have no symptoms.

1st phase: viraemic phase.

Symptoms occur at the end of first week:
- fever, malaise, myalgia, chills, itching.
- erythematous rash, most intense on cheek – ‘slapped cheek disease’

2nd phase: 
- mediated by immune complexes.
- rash on body and limbs become maculopapular.
- mild lymphadenopathy.
- arthralgia with swelling and pain in joints, esp. in women.
- resembles rubella.

Complications:
- Aplastic crises in children with chronic hemolytic anemia.
- non-immune hydrops fetalis: affect fetus during maternal infection; cause severe fetal infection and death with fall in hemoglobin level.
- Immunodeficiency: chronic anemia 	Serology:
- ELISA for IgM
- IgM appears 4-7 days
- IgG appears 7-10 days later, persist for years.

Direct demonstration of viral DNA in tissues and blood, by PCR and DNA probe.	No antiviral therapy available.

Blood transfusion in transient aplastic crises.

Fetal infection:
- conservative management.
- high-dose IgG therapy.
- intrauterine fetal transfusion.