Parvovirus B19

Parvovirus B19 is a DNA virus which causes a variety of clinical presentations. It was identified in the 1980's as the cause of erythema infectiosum

Erythema infectiosum (also known as fifth disease or 'slapped-cheek syndrome')

The illness may consist of a mild feverish illness which is hardly noticeable. However, in others there is a noticeable rash which appears after a few days. The rose-red rash makes the cheeks appear bright red, hence the name 'slapped cheek syndrome'. The rash may spread to the rest of the body but unlike many other rashes, it only rarely involves the palms and soles.

The child begins to feel better as the rash appears and the rash usually peaks after a week and then fades. The rash is unusual in that for some months afterwards, a warm bath, sunlight, heat or fever will trigger a recurrence of the bright red cheeks and the rash itself. Most children recover and need no specific treatment. School exclusion is unnecessary as the child is not infectious once the rash emerges. In adults, the virus may cause acute arthritis.

Be aware that the virus can affect an unborn baby in the first 20 weeks of pregnancy. If a woman is exposed early in pregnancy (before 20 weeks) she should seek prompt advice from whoever is giving her antenatal care as maternal IgM and IgG will need to be checked. It is spread by the respiratory route and a person is infectious 3 to 5 days before the appearance of the rash. Children are no longer infectious once the rash appears and there is no specific treatment.

The child need not be excluded from school as they are no longer infectious by the time the rash occurs.

Other presentations

Other presentations include:

• asymptomatic
• pancytopaenia in immunosuppressed patients
• aplastic crises e.g. in sickle-cell disease
  • parvovirus B19 suppresses erythropoiesis for about a week so aplastic anaemia is rare unless there is a chronic haemolytic anaemia
• hydrops fetalis
  • parvovirus B19 in pregnant women can cross the placenta in pregnant women
  • this causes severe anaemia due to viral suppression of fetal erythropoiesis → heart failure secondary to severe anaemia → the accumulation of fluid in fetal serous cavities (e.g. ascites, pleural and pericardial effusions)
  • treated with intrauterine blood transfusions

Exposure in Pregnancy

Parvovirus B19 is infectious from up to 3 weeks before the rash develops. It is no longer infectious once the rash appears. The risk of transmission increases with gestational age.

Immediate serological testing for parvovirus B19 is required for all pregnant women in contact with someone with a rash consistent with parvovirus. Significant contact is defined as face-to-face or in the same room for more than 15 minutes in the 3 weeks before the index case developed a rash. It is also important to ensure the pregnant woman is immune to rubella.

Blood should be tested for parvovirus B19 specific IgM and IgG.

• IgG positive & IgM negative - shows immunity to parvovirus. Reassure, no further action.
• IgG negative & IgM positive - non-immune. Recent parvovirus infection in last 4 weeks. Refer immediately for further tests/fetal medicine.
• IgG negative & IgM negative - repeat test in 4 weeks. If both tests still negative, this confirms susceptibility, but no recent infection. Reassure, further action required only if subsequent exposure occurs.