What is Parvovirus (Fifth Disease)?
Parvovirus infection, also known as erythema infectiosum or “fifth disease,” is a viral illness caused by the Parvovirus B19.
What are the symptoms?
General symptoms typical of viral infections include malaise, weakness, muscle aches, and fever.
In children, a symmetrical rash usually appears on the cheeks (giving the “slapped cheek” or “butterfly” appearance), often spreading to the trunk and limbs in a lace-like, itchy pattern.
In adults, rashes are less common; joint pain and swelling are more typical, lasting one to two weeks.
How is it transmitted?
Parvovirus B19 spreads primarily through respiratory droplets.
An infected person becomes contagious about six days after exposure, remaining infectious for roughly a week – usually until the rash or joint symptoms appear.
If living in the same household as an infected person, the risk of transmission is about 50%; in a shared classroom or daycare group, it’s around 20-30%.
Between 30-60% of adults have already had the infection and carry antibodies against Parvovirus B19, meaning reinfection is extremely rare.
Pregnant women are equally susceptible to infection as non-pregnant adults; the incidence during pregnancy is around 3.3-3.8%.
How is it treated?
Parvovirus B19 is usually a mild viral illness requiring only symptomatic treatment (such as fever reducers or antihistamines).
Is it dangerous for expectant mothers?
The infection itself does not cause congenital malformations, but it can sometimes lead to miscarriage or fetal death.
Before 20 weeks: 11% (13% in the first trimester, then 9%)
After 20 weeks: less than 1%
In the third trimester: extremely rare (0.02%)
Why can Parvovirus be dangerous to the fetus?
Parvovirus B19 can attack fetal red blood cells, leading to anemia and, in some cases, hydrops fetalis (fluid accumulation in fetal tissues and cavities).
Hydrops usually appears within three weeks after infection, but in 93% of cases, within eight weeks.
Hydrops may resolve spontaneously, and in some cases can be treated with intrauterine blood transfusion, so it does not always result in fetal death.
Babies who recover from Parvovirus B19 infection do not have an increased risk of congenital abnormalities.
I’m pregnant and was exposed to Parvovirus – what should I do?
Blood tests for Parvovirus B19 IgG and IgM can determine whether the mother has had a previous infection or has recently been infected.
If IgM is negative and IgG is positive – the mother had the infection previously, and no further action is needed.
If both IgM and IgG are negative – the test should be repeated in one month; if still negative, there is no immunity, but also no infection, so no further steps are necessary.
If IgM is positive, additional tests (such as more frequent ultrasound monitoring) are required.
Source:
Riley, L.E.& Fernandes, C.J. (2024). Parvovirus B19 infection during pregnancy. In T.W. Post, Hirsch, M.S., Edwards, M.S., Lockwood, C.J., Bogorodskaya, M.& Barss, W.A. (Eds.), UptoDate. Available from https://www.uptodate.com/contents/parvovirus-b19-infection-during-pregnancy