Polioviruses have been detected in wastewater in several German cities, prompting the Robert Koch Institute (RKI) and the German Society of Neurology (DGN) to issue increased warnings about vaccination gaps. The pathogens, known as circulating vaccine-associated poliovirus type 2 (cVDPV2), originate from mutated vaccine viruses that can become pathogenic again, especially in people without adequate vaccination protection. Although experts do not see a risk of widespread spread, they believe that local transmission is increasingly likely. Children under the age of five and immunocompromised adults are particularly at risk. The DGN and the RKI are urgently calling for vaccination status to be checked and hygiene measures such as thorough hand washing to be reinforced in order to minimize the risk of infection with the dreaded polio.

Poliomyelitis, colloquially known as polio, is a highly contagious viral infection that attacks the central nervous system and can lead to permanent paralysis. Although the current situation is a setback, immunization in Germany is so high that there is no need to fear an endemic, explains Prof. Dr. Uta Meyding-Lamadé, member of the DGN Commission on Neuroinfectiology and deputy chair of the National Polio Commission of the RKI. Nevertheless, she warns: “However, we must assume that children without vaccination protection and immunocompromised adults without vaccination protection could now also become infected with polioviruses again in Germany.” The detections in wastewater that have been made since the end of 2024 in cities such as Munich, Dresden, Hamburg, Cologne, Bonn, Düsseldorf, Mainz, Berlin and Stuttgart indicate that the virus is circulating locally, presumably through human-to-human transmission.

Transmission mainly occurs through smear infection, where the viruses are excreted in the stool and passed on via contaminated hands or surfaces. “The viruses are excreted with the stool – and are often passed into the hand with the handle. Regular hand washing and hand disinfection minimize the risk of transmission,” emphasizes the RKI. In most cases, an infection is asymptomatic, but severe neurological complications can occur in around one in 200 infected people. The disease goes through three phases: First, fever and headaches occur, followed by the paralytic stage with typical asymmetrical paralysis due to damage to the spinal cord. In the repair stage, these paralyses often only partially recover. “A good third of those affected suffer severe, permanent paralysis,” says DGN Secretary General Prof. Dr. Peter Berlit. Late effects such as post-polio syndrome with fatigue and pain or spinal muscular atrophy increase the risk of further paralysis.

The cVDPV2 variant found in wastewater originates from the oral polio vaccine (OPV), which has not been used in Germany since 1998, but is still used in some countries. These attenuated vaccine viruses can spread in the population at low vaccination rates, change genetically and become pathogenic again. The RKI suspects that the viruses were introduced by travelers from regions such as Africa, where cVDPV2 has been circulating since 2020. “Given the long duration of the event and the detection of cVDPV2 at various locations, it seems increasingly likely that at least localized transmission of cVDPV2 between humans is taking place,” explains the RKI in its Epidemiological Bulletin.

Vaccination remains the most effective form of protection. The Standing Committee on Vaccination (STIKO) recommends a basic immunization for infants aged 2, 4 and 11 months and a booster vaccination between 9 and 16 years. Adults without complete basic immunization should catch up on this, whereby three doses are required at least six months apart between the second and third vaccination. “It is important to check the vaccination status of children. There are always cases in which vaccination appointments are not kept for various reasons and the children are not sufficiently protected,” says Meyding-Lamadé. Particularly alarming: According to the RKI, only 21 percent of one-year-old children are fully protected with three vaccine doses, far below the target vaccination rate of 95 percent.

Immunocompromised adults, for example due to immunosuppressants or diseases such as leukemia, are also at risk. “There is no need to panic, as adults are infected much less frequently and only in exceptional cases do severe cases occur. Nevertheless, unvaccinated people in this risk group should consider getting vaccinated,” advises Meyding-Lamadé. Vulnerable groups in particular, such as refugees in shared accommodation or people from crisis areas where vaccination programs have been interrupted by conflicts such as in Gaza or Ukraine, should check their vaccination status.

The treatment options for polio are very limited. “The only option is the administration of immunoglobulins, but their effectiveness has not yet been sufficiently proven. This makes it clear how important prophylaxis through vaccination is,” emphasizes Berlit. Wastewater monitoring has proven to be an effective early warning system, but the findings show that vigilance is required. “Although we do not have an alarming situation in Germany, we are now once again seeing evidence of a virus that we assumed had been eradicated in our country. We therefore need to strengthen the protection of vulnerable groups,” says Meyding-Lamadé. In addition to vaccinations, thorough hand hygiene remains a simple but effective measure to contain the spread of polioviruses.

_{Editorial office: X-Press Journalistenbüro GbR}

Gender note. The personal designations used in this text always refer equally to female, male and diverse persons. Double/triple references and gendered designations are avoided in favor of better readability.