No 10 - 2011

Parvovirus B19 and pregnancy

Fifth disease (or Erythema Infectiosum) is caused by parvovirus B19 infection and is a common and generally mild childhood disease which occurs worldwide. Its signature symptom is a red rash starting at the cheeks.

Five to ten days ("1 week") after infection, the person starts excreting virus to airway secretions, and the rash does not present until 13-18 days ("2 weeks") after the time of infection, at which point the person is non-infectious. The rash may be preceded by mild influenza-like symptoms.

In 20-30 % of cases, the infection is subclinical. Many cases of infection thus occur without any medical intervention. Infection produces life-long immunity.

Other manifestations of the disease include long-lasting joint-related symptoms.

In patients with haematological conditions, the disease may run a more serious course and such patients may excrete virus for long periods and in great quantities.

In Denmark, the infection lies at a low endemic level with bursts of spring epidemics approx. every third year.

Foetus risk

Two thirds of all females are immune to the condition, meaning that both the pregnant woman and the foetus are immune to the infection.

Whether sero-negative pregnant women are infected depends on the infection pressure which in Denmark has been found to be approx. 13 % during epidemics and approx. 1.5 % in non-epidemic contexts.

If the pregnant woman is infected, the infection may be transferred to the foetus. This occurs with increasing frequency throughout the pregnancy, but it hardly ever has any consequences to the child when the infection occurs after week 20.

If the foetus is infected, there is a risk of abortion/foetal death or of developing foetal hydrops due to the anaemia which may occur.

A major English study found:

• Abortion/foetal death in 9 % of the pregnant women who were infected before or during week 20. (Primarily after infection occurring between week 9 and week 16).
• Foetal hydrops in 2.9 % of the pregnant women who acquired the infection between week 9 and week 20 and were diagnosed 2-17 weeks after infection occurred.

Based on the above data, the risk of infection and the known immunity share, calculations show that an average of 35 cases of abortion/foetal death and 5-10 cases of hydrops will occur annually in Denmark.

Hydrops occur at various degrees of severity. The degree may be monitored with non-invasive ultrasound.

Only in very rare cases will the condition develop to a severity requiring a Caesarean or intrauterine blood transfusion.

Malformations have not been observed in connection with parvovirus B19 infection.

Infection and prophylaxis

Parvovirus B19 is found in families with children, at nurseries and schools etc. but may occur anywhere.

Infection precedes symptom presentation and subclinical infections are frequent, consequently targeted prophylaxis is difficult to implement.

Parvovirus B19 is transferred via airway secretions and through contact and droplet infection.

Good hygiene including thorough and frequent hand-washing may help prevent infection.

No vaccine is available to counter infection.

Right to absence from work due to risk to the child?

The National Board of Health has determined that the value of affording the pregnant woman a right to absence from work due to the risk to the child is very limited and, furthermore, causes a number of problems.

Consequently, the National Board of Health does not recommend that pregnant women are afforded such absence due to parvovirus B19 infection in their surroundings, unless extraordinary causes support such measure (e.g. maternal blood condition).

The Danish Working Environment Authority refers to the National Board of Health's provisions with regard to absence from work due to parvovirus B19.

Suspicion of transfer or infection in pregnant women

It is essential that the pregnant woman be informed on suspicion of infection:

• If the pregnant woman has been infected prior to the pregnancy, there is no risk to the foetus.
• If the pregnant woman was in the final half of her pregnancy at the time of the infection, the risk to the infant is extremely low. However, the physician shall take into account any uncertainties regarding the presumed time of infection and calculation of the pregnancy term.
• If the pregnant woman is in the first half of her pregnancy (up to and including week 20), she should be informed that there is a limited risk to the foetus, she should also be informed that malformations do not occur and she should be offered an IgM and IgG antibody test for parvovirus B19 and follow-up according to the following guidelines:
  • IgM negative and IgG positive:
    The woman is immune and there is no risk of reinfection.
  • IgM negative and IgG negative:
    The woman should be offered another test 2-3 weeks after exposure.
  • IgM positive:
    The woman has recently been infected and should be referred to a specialist department.

The above information and a letter with information to the pregnant woman are available at the homepage of the National Board of Health.

For further information, please refer to www.at.dk and www.ssi.dk.

(Danish National Board of Health)

Revaccination against Japanese Encephalitis

The Department of Epidemiology currently receives many questions concerning revaccination against Japanese encephalitis (JE).

The primary vaccination series consists of two vaccines (Ixiaro®) which should be given at a four-week interval.

In case of renewed or continued exposure to JE, a booster dose of Ixiaro® should be given 12-24 months after the primary series, EPI-NEWS 25/10.

The duration of the protection provided by the booster dose remains unknown. However, there is no reasons to believe that its duration is shorter than the three years observed for the other JE vaccines.

(Department of Epidemiology)

Individually notifiable diseases and selected laboratory diagnosed infections (pdf) 

9 March 2011