National Reference Center for Poliomyelitis and Enteroviruses (NRZ PE)

Head:

Sabine Diedrich

Deputy:

Sindy Böttcher

Together with its partners in the Global Polio Eradication Initiative (GPEI) - Unicef, Rotary International and the US health authorities CDC - the WHO has succeeded in largely eliminating poliomyelitis (polio).

Vaccination programs implemented worldwide since 1988 have reduced the number of polio cases by more than 99.9%. Poliomyelitis is endemic only in Afghanistan and Pakistan (as of December 2023). However, wild polioviruses can be introduced from there (e.g. by migrants or travelers) into regions that are already polio-free. The prerequisite for certification is the absence of illnesses caused by wild polioviruses for at least three years in a region, combined with good quality surveillance. Five of the six WHO regions are already considered polio-free. The American continent was certified in 1994, followed by the Western Pacific region in 2000. Europe has been free of indigenous poliomyelitis since June 2002. Southeast Asia was also declared polio-free in 2014. Although the African continent has been considered free of wild polioviruses since 2020, there were renewed introductions in 2021/2022 (Malawi, Mozambique).

In addition, Vaccine-derived polioviruses (VDPVs) are also frequently detected, particularly in Africa. These occur through the circulation (and associated mutation) of vaccine viruses in population groups with inadequate vaccination coverage. Under these conditions, undetected circulation of polio vaccine viruses can also occur in countries that only use the inactivated polio vaccine (IPV) (e.g. Israel).

The global polio eradication program includes not only the consistent implementation of vaccinations but also the monitoring of poliovirus circulation (surveillance) and laboratory containment. The following methods can be used to monitor the polio situation:

• Testing of stool samples from patients with acute flaccid paralysis (AFP surveillance)
• Additional enterovirus surveillance (syndromic, laboratory-based)
• Additional testing of wastewater samples

The last indigenous case of polio in Germany was in 1990. After the imported diseases caused by wild polioviruses from India and Egypt in 1992, up to three vaccine-associated paralytic polio cases were registered in the following years (so-called VAPP cases due to live vaccine). In 1998, the switch was made to the inactivated vaccine (IPV).

The National AFP Surveillance was established as a polio-free surveillance system under the leadership of the Lower Saxony State Health Office in Hanover and carried out between 1998 and 2010. However, as the results of AFP surveillance were inadequate, an alternative polio-free surveillance system was also introduced. As part of enterovirus surveillance (EVSurv), all pediatric and neurological clinics in Germany have been offered free enterovirus diagnostics for the differential diagnosis of viral meningitis/encephalitis since 2006. A laboratory network for enterovirus diagnostics in Germany (LaNED) coordinated by the NRZ PE was established for this purpose. For quality assurance, proficiency tests are performed bi-annually for detection of enteroviruses by virus cultivation and typing as well as by genome detection (PCR).

The results of the laboratory and epidemiological tests are recorded and evaluated by the office of the National Commission for Polio Eradication in Germany at the RKI and reported to the WHO in anonymized form.

As part of nationwide enterovirus surveillance, the NRZ PE primarily carries out further enterovirus characterization. The network laboratories should send all samples to the NRZ PE for further analysis, including

• non-typable enteroviruses
• PCR positive and culture negative samples as well as
• suspected polioviruses

The aim is to exclude polioviruses in these samples or to characterize their origin (vaccine/vaccine-derived/wild virus) by means of sequence analyses in various genome regions.

The NRZ PE also acts as a regional WHO reference laboratory for poliomyelitis and is primarily responsible for the sequencing of polioviruses.

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