Parvovirus

• Common childhood virus that usually causes a benign, self-limiting infection.
• Often asymptomatic, but can present with non-specific flu-like illness, rash illness (‘slapped cheek’), or arthralgias (more common in adults).
• Can cause serious infection in those with chronic haemolytic disorders, severe immune compromise, or serious congenital infection in non-immune pregnant women. If fetal infection occurs, can cause ‘hydrops fetalis’. Doesn’t cause other types of fetal abnormalities.

Infection reduces/halts red blood cell production until immune response. In healthy people this doesn’t cause any problems, but in those with shortened red cell lifespan e.g. chronic haemolysis, can cause severe anaemia.

Laboratory confirmation of infection not required for the vast majority of cases.

• Seek specialist advice if suspected infection in people with haematologic disorders or severe immune compromise.
• Test pregnant women with possible symptoms of parvovirus infection.
• Test for immunity in pregnant women with possible exposure to parvovirus.
• Seek specialist advice if suspected congenital infection (hydrops on USS). Polyhydramnios or other abnormalities without features of hydrops are not usually indications for testing.

Request Parvovirus serology

Parvovirus IgM is a marker of primary (acute) infection. Usually detectable at onset of symptoms. May persist for several months.

• Reasonable sensitivity – a negative result makes the diagnosis unlikely.
• Reasonable specificity – a positive result supports, but doesn’t confirm infection.

Parvovirus IgG indicates infection at some point in time (can be acute or past infection). Usually appears within a few days of symptoms.

• Excellent sensitivity – a negative result excludes infection if more than a few days of symptoms.
• Excellent specificity  – a positive result confirms infection at some stage.
  • Infers immunity in a pregnant woman tested within a few days of exposure to possible parvovirus.
• Conversion from negative to positive IgG confirms acute infection during the intervening period.

Parvovirus PCR is reserved for specialist use, e.g.:

• Diagnosis of infection in severe immune compromise – antibody tests less reliable.
• Confirmation of infection in certain situations where serology is inconclusive.