Clinician Information

The Virus

What is it?

• Discovered in 1975 in asymptomatic blood donors.
• Small DNA virus (parvum being Latin for small).
• Parvovirus B19 only infects humans.
• Causative agent of erythema infectiosum (fifth disease of childhood).

What is the seroprevalence of Parvovirus B19?

• Approximately 60%(1,5).

How is it spread?

• Transmission is greatest during viremia and before symptoms arise.
• The virus is spread via aerosol droplets through the respiratory route.
• Transmitted by hand-to-mouth contact, blood or blood products and nosocomial infection.
• Can be spread transplacentally to the fetus during active maternal infection (33% transmission rate across the placenta)(2).
• During outbreaks, infection rates of 25 and 50% have been noted in the school and home, respectively(3).

• Parvovirus B19 infection can occur at any time .
• The majority of outbreaks tend to be in the Winter and Spring time.

What cell types are infected?

• Preferentially Parvovirus B19 infects and replicates in erythroid cells.
• Following Parvovirus B19 infection, erythrocytes will lyse arresting erythropoiesis.
• Lymphocyte, granulocyte and platelet counts may also fall during infection.
• The B19V incubation period is usually 4-14 days.

Who is at risk of infection?

• All non-immune individuals (up to 50% of the population)
• A higher risk of infection exists in school and child care personnel.

Who is at risk of complications due to infection?

• Pregnant women and their fetuses.
• Highest risk of infection for pregnant women is during epidemics and following exposure to infected children in the home(4).
• Persons with pre-existing anemia and congenital or acquired immunodeficiencies.

What is the incidence of infection in pregnant women?

It has been estimated that maternal Parvovirus B19 infection occurs in approximately 1 in every 400 pregnancies(5).

Can Parvovirus B19 infection be treated?

• High titre immunoglobulin treatment has been shown to be effective against the virus.
• The clinical manifestations of Parvovirus B19 infection can also be treated through intrauterine transfusion.
• Work is being carried out at present to produce a vaccine for B19V.

What is the immune response following Parvovirus B19 infection?

• IgM antibodies are present in 90% of patients approximately 2 weeks after infection.
• IgM levels can peak around 30 days post- infection and may last up to 4 months.
• IgG antibodies start to appear after 3-4 weeks and most probably persist for life(6).

References

1. Hedrick J. The effects of human parvovirus B19 and cytomegalovirus during pregnancy.
   J Perinatol Neonat Nurs. 1996; 10:30-39.
   
2. Public Health Laboratory Service Working Party of Fifth Disease. Prospective study of human parvovirus (B19) infection in pregnancy. Br J Med. 1990; 300:166-70.
   
3. Anderson LJ, et al. Risk of infection following exposures to human parvovirus B19. Behring Inst Mitt. 1990; 85:60-3
   Valeur-Jensen AK, et al. Risk factors for parvovirus B19 infection in pregnancy. JAMA 1999; 281:1099-105.
   
4. Gay NJ, et al. Age Specific Antibody Prevalence to parvovirus B19: How many women are infected in pregnancy? Communicable Disease Report 1994;4:104-107.
   
5. Eis-Hübinger AM, et al. Parvovirus B19 infection in pregnancy. Intervirology 1998;41:178-84.