Poliovirus detections in European Region underscore importance of vaccination and vigilance

28 November 2024, Copenhagen

Poliovirus has been detected through routine surveillance of wastewater systems in 3 countries in the WHO European Region (Germany, Poland and Spain) since September this year. While no cases have been detected to date, the presence of the virus underscores the importance of vaccination and surveillance, as well as the ongoing risk that any form of poliovirus poses to all countries everywhere.

"These countries are to be commended for their strong vigilance, which enabled them to detect and quickly respond to this public health threat," said Robb Butler, Director of the Division of Communicable Diseases, Environment and Health at WHO/Europe. "While investigation of these detections is ongoing, WHO will continue to work with all countries in the Region to strengthen poliovirus surveillance and ensure high immunization rates."

The Region has been free of endemic poliomyelitis (polio) since 2022. However, as long as any form of poliovirus is spreading anywhere in the world, it can be imported. Such importations can lead to outbreaks if the virus finds its way to unvaccinated individuals, as occurred in Tajikistan and Ukraine in 2021, and Israel and the United Kingdom in 2022.

All countries in the Region are on alert for such importations and many conduct routine surveillance of sewage systems to ensure early detection. Consistently high rates of vaccination are vital to prevent the virus from re-establishing a foothold in any community.

Detections in 2024

In the past 3 months, circulating vaccine-derived poliovirus type 2 (VDPV2) was detected in sewage samples in Barcelona, Spain; Warsaw, Poland; and Cologne, Bonn, Hamburg and Munich, Germany. The detected virus is genetically linked to a strain that emerged in Nigeria. This strain is circulating in several countries outside the Region, most widely in North and West Africa.

In all 3 countries in the European Region, the virus was isolated from environmental (sewage) samples only - no associated paralytic cases of polio have been detected.

"WHO continues to support national and local public health authorities in their investigations and monitoring of the situation, including identification of any potential subnational immunity gaps that may need to be addressed," added Robb Butler. "Vaccination of every vulnerable child is essential to ensure that the virus cannot lead to lifelong paralysis or even death."

Germany, Poland and Spain maintain strong disease surveillance and high levels of routine immunization coverage, estimated at 85-93% nationally with 3 doses of inactivated polio vaccine (IPV), which provides excellent protection from paralysis caused by poliovirus.

However, pockets of undervaccination exist in every country. In response to the detections, investigations are ongoing, including through continued disease surveillance. Subnational immunity levels have been examined to identify any potential gaps and immunization of unvaccinated children has been initiated.

Polio eradication

Polio is a highly infectious disease that travels easily and silently across wide geographic areas, not respecting national borders. These detections are a further reminder of the urgent need to eradicate all forms of poliovirus.

WHO/Europe, together with other Global Polio Eradication Initiative partners, is continuing to support national and local public health authorities in their investigations and monitoring of the situation, as well as in rapid response to detections of the virus to prevent it from spreading.