The number of reported cases of rubella has increased significantly in Germany and several other EU countries since the beginning of the year. Although infections with the parvovirus B19 (B19V) usually only occur more frequently in spring and early summer, there was already a significant increase in incidence in this country between January and March, says Martin Enders from the consulting laboratory for parvoviruses in Stuttgart. Infection poses a risk, especially for pregnant women.

As a result of the very high incidence, B19V-related fetal complications during pregnancy such as miscarriages (abortion) and fluid accumulation (hydrops) are increasingly being reported, says Enders. The following non-representative case numbers, diagnosed in the Stuttgart laboratory (as of April 26th), were counted for the first three months of the year: more than 120 cases in January, around 150 in February and more than 240 in March. According to Enders, the complications most often occur in infections before the 20th week.

Once sick – forever immune

Rubella is very contagious. Infection occurs through droplets containing pathogens that are spread through coughing, sneezing or contaminated hands. The viruses can also spread through smear infections – possibly even through door handles. Most adults and children experience flu symptoms such as a mild fever with swelling of the lymph nodes. The typical skin rash does not always develop.

There is a risk of infection for people who have not yet had rubella. Anyone who has survived the infection is protected for life and will not become ill again. According to Enders, pregnant women most often become infected from children, usually in their own household or through occupational exposure.

There is a risk of miscarriage or premature birth

Pregnant women pass the rubella pathogens on to their unborn child, even if the infection goes unnoticed. The viruses enter the child’s bloodstream via the placenta and attack blood-forming cells – the result can be anemia in the unborn child. In the worst case, there is a risk of miscarriage or premature birth, especially in the first months of pregnancy.

“Some pregnant women show typical symptoms such as coughing, a runny nose and then a rash. But this is not always the case,” says the federal spokesman for the professional association of pediatricians and adolescents, Jakob Maske. There are hardly any similar diseases that lead to a rash as specific as that caused by rubella. “Of course there are allergic reactions that can look similar. But they usually have other symptoms.”

Have you ever been infected? A test shows this

Karl Oliver Kagan, head of prenatal medicine at the University Women’s Clinic in Tübingen, also speaks of many pregnant women who are currently infected with parvovirus B19 and come to the clinic for treatment or check-ups. However, it cannot be said how many people are actually infected because not everyone affected developed symptoms.

If a pregnant woman wants to know whether she has ever had rubella in the past and is possibly immune, she can get tested – for example if there has been contact with an infected person. This test looks for antibodies against the parovirus B19 and, if necessary, for virus genetic material in the blood.

Hardly any chance of action in the first few weeks

According to Kagan, if the mother is infected with rubella, it is assumed that around ten percent of the unborn children will become infected. In pregnant women who were infected in the first half of pregnancy, it should be clarified whether the infection is causing childhood anemia.

“In the case of anemia, the unborn child needs a blood supply that can be administered externally via the umbilical cord. Given the small diameter of the umbilical cord, this therapy is challenging and is actually only possible from the 16th week of pregnancy,” says Kagan. After hardly any transfusions had to be carried out in the Tübingen women’s clinic in recent years due to rubella infections, there are now around two per week.

In the first weeks of pregnancy, there is no way to detect an infection or anemia in the embryo. In some cases, anemia can be detected in the first trimester screening in the twelfth or thirteenth week of pregnancy, but it is still too early for a blood transfusion. “An infection in the last third of pregnancy does not usually pose a life-threatening risk to the unborn child,” explains Kagan.

Where does the increase come from?

According to Enders, the exceptionally strong activity can be explained, among other things, by the fact that the number of cases was very low during the pandemic due to lockdowns and hygiene measures and that there is now a significantly higher number of susceptible hosts available to the virus. “From the beginning of 2020 to the beginning of 2023, we had no activity or only minimal activity for three years.

That means a lot of children have accumulated who are not immune and that’s what’s going on now,” says Enders. More infections in children automatically mean more infections in pregnant women – and with that more complications. “But I don’t think so “That the virus has somehow changed and that the infections are therefore more severe.”

The EU health authority ECDC recently reported an increase in the number of parvovirus B19 infections in Denmark, Ireland, the Netherlands, Norway and France. Although a detailed epidemiological analysis is lacking because the disease is not monitored in most countries, the data showed increased infection rates in several age groups, with young children particularly affected. In addition to pregnant women, the risk groups for serious illness included people with blood disorders or immunosuppression (immune deficiency).