The World Health Organization has reiterated that the spread of poliovirus remains a Public Health Emergency of International Concern for several months.
This concern was further validated in late 2024 when vaccine-derived poliovirus type 2 (VDPV2), genetically linked to the Nigeria lineage, was found in wastewater samples from 16 cities across five European countries—Spain, Poland, Germany, the United Kingdom, and Finland.
On March 6, 2025, the US CDC reported that the presence of VDPV2 in wastewater indicates the virus’s importation into these countries. However, no human polio cases or infections have been associated with these detections so far.
Genetic sequencing confirmed a link to the cVDPV2 NIE-ZAS-1 virus, first detected in Zamfara, Nigeria, in July 2020, which remains in circulation. In 2024, Nigeria reported 94 confirmed polio cases across 15 states, though no type 2 variant poliovirus cases have been confirmed in 2025.
The spread of cVDPV2 has triggered poliomyelitis outbreaks in 15 countries across North and West Africa and has been detected in six additional African nations.
Last week, the Global Polio Eradication Initiative confirmed polio cases in five countries, including Pakistan, which reported three Wild Polio cases and 28 WPV1-positive environmental samples.
In response to these risks, the CDC reissued a Global Polio Alert—Level 2 on January 15, 2025, advising enhanced precautions for travelers to 39 affected countries. The agency noted that these countries are actively vaccinating targeted populations to curb the virus’s spread.
To combat polio globally, two vaccines are used: oral poliovirus vaccine (OPV) and inactivated poliovirus vaccine (IPV). The U.S. has exclusively used IPV since 2000. Additionally, over the past few years, nearly 1 billion doses of nOPV2 have been administered worldwide.
Ensuring sustained polio vaccination efforts, Saudi Arabia has reaffirmed its $500 million pledge, aiming to immunize 370 million children annually.
This situation underscores the ongoing risk of VDPV outbreaks and highlights the urgent need for intensified global efforts to eradicate all poliovirus strains. The CDC advises prospective travelers to consult a travel vaccine expert at least one month before international travel to discuss polio immunization options.
