Parvovirus

Parvovirus

Parvovirus B 19 is the causes of slapped cheek syndrome (erythema infectiosum) in children.

Transmission

Transmission is mainly through respiratory route.

Rarely transmit through blood products.

Patients with skin rashes are not infectious.

Incubation period

The incubation period ranges between 12 to 18 days.

Infectious period- 7 days before the onset of rash until the onset of rash

Clinical presentations

Fever

Upper respiratory symptoms

Skin rash- macular

In children- erythematous rash on the cheeks.

Joint pain in adult patients, especially in women.

There are three groups of patients where the effect of infection is significant

The classic signs and symptoms are skin rash and arthralgia (joint pain).

1. In patients with haematological disorders (Patients with haemoglobinopathies)

As their immune systems are functional, they usually have the characteristic features of Parvovirus infections.

The main problem with these group of patients is severe anaemia. Parvovirus infects red blood cells (RBC) and for this reason it would cause severe anaemia as these groups of patients would have mild anaemia, or RBC cell counts on the lower side of the normal ranges before infection.

Unlike immunocompromised patient, chronic infection is uncommon.

2.In Immunocompromised patients

Mostly present with chronic anaemia.

Infection may persist for longer.

May present with classic signs and symptoms.

3. In pregnant women

The infection may not be symptomatic.

The risk to the foetus is only if the mother is infected in the first 20 weeks of gestation.

Among the complications, missed abortion is common.

Infection with Parvovirus does not cause congenital abnormality or defect. It may, however, cause severe anaemia that may result in congestive heart failure in the unborn baby (hydrops fetalis)

Investigation

Depending on the clinical presentations.

CBC- anaemia, and increase in reticulocyte number.
Bone marrow biopsy
Ultrasound

Diagnostic tests

Immunocompetent patient.

Serum for Parvovirus IgM-it is useful to diagnose acute/recent infection.

Anaemia in patients with haemoglobulinopathies

Serum should be sent for Parvovirus IgM- some patient may not produce detectable level of Parvovirus IgM for a few weeks. PCR for Parvovirus may help to exclude Parvovirus B 19 infection.

Chronic anaemia in immunocompromised patients

Blood in EDTA or bone marrow biopsy for Parvovirus PCR should be sent. In this group of patients the antibody may not be detectable at the time of infection.

Be careful when you interpret Parvovirus IgM positive result as it may remain detectable for several weeks to months, in some up to a year.

Congenital abnormality

Testing for Parvovirus is not required. It does not cause congenital defect.

Hydrops fetalis

When hydrops fetalis is detected with routine ultrasound examination, the mother blood should be tested for Parvovirus IgM .

Missed abortion

Test the mother blood for Parvovirus IgM or

- if Parvovirus is strongly suspected- tissue biopsy for Parvovirus PCR

Investigation of mothers exposed to Parvovirus B 19 infection (PDF)

Screening test is not routinely done. However screening patients with haemoglobinopathies or immunosuppression may be important to establish immunity as re-infection is uncommon.

Treatment

Antipyretics may be needed to treat patients with high grade fever.

Anaemia if severe can be treated with blood transfusion.

Chronic anaemia in immunocompromised patient should be treated with blood transfusion. In addition Human Normal Immunoglobulin should be given monthly to neutralise the virus particles in the blood.

Intrauterine blood transfusion has been used to treat foetus with hydrops fetalis. Nevertheless intrauterine blood transfusion is associated with high foetal loss.

Prevention

There is no specific measure.

There is no vaccine.

Although the risk to pregnant healthcare workers is well recognised, in practise avoiding contact with patients who have Parvovirus infection is not possible due to the fact that there is no way of knowing a patient who is infectious.

Screening of immunocompromised patients may beneficial. Those susceptible individuals may be advised to have follow up for infection. This may be particularly useful for HIV infected patient as anaemia is the common problem.