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Recent detections of poliovirus in wastewater in Spain, Germany, and Poland have raised alarms across Europe. While this discovery does not confirm infections in the population, it serves as a critical reminder of the persistent threat polio poses and the importance of maintaining robust vaccination coverage.
Polio: A Persistent Threat Polio, or poliomyelitis, is an extremely contagious disease caused by the poliovirus. It attacks the nervous system and can lead to full paralysis within hours. The virus enters through the mouth and multiplies in the intestine, spreading through the fecal-oral route. Approximately one in every 200 infections results in irreversible paralysis, often affecting the legs, with 5–10% of paralyzed individuals dying due to immobilized breathing muscles.
Since the World Health Organization (WHO) called for the global eradication of polio in 1988, the number of poliovirus cases has decreased by over 99%. Today, only Pakistan and Afghanistan are considered endemic for polio. However, the recent detection of poliovirus in European wastewater is a wake-up call, highlighting potential vulnerabilities in vaccination coverage.
Wastewater Surveillance: A Key Tool The detection of poliovirus in wastewater does not necessarily indicate active infections but can signal potential risks. Wastewater surveillance, an approach reinvigorated during the COVID-19 pandemic, has proven invaluable for early detection of disease outbreaks. Analyzing wastewater can provide public health officials with critical insights, allowing them to take preventative measures.
Routine testing in Spain, Germany, and Poland revealed a specific vaccine-derived poliovirus strain. While no polio cases were reported in these countries, the presence of the virus in wastewater underscores the importance of maintaining high vaccination rates to prevent outbreaks.
Vaccine-Derived Poliovirus Vaccine-derived poliovirus strains can emerge from the weakened live poliovirus used in oral polio vaccines. If this weakened virus circulates long enough among under-immunized groups or individuals with weakened immune systems, it can revert to a form capable of causing disease.
Inactivated polio vaccine (IPV) offers an alternative that cannot revert to a dangerous form. However, IPV is more expensive and complex to deliver, often limiting its use in poorer countries with greater vaccination needs. Despite these challenges, oral polio vaccines have been instrumental in eradicating certain poliovirus strains globally.
Maintaining Vigilance In 2023, polio immunization coverage for one-year-olds in Europe stood around 95%, above the 80% threshold for herd immunity. However, under-immunized groups and individuals with weakened immune systems remain at risk. Ensuring widespread, sustained vaccination is essential to prevent polio’s resurgence.
The progress in polio eradication over the past three decades is a testament to global efforts. However, mounting humanitarian crises, conflict, natural disasters, and climate change are disrupting vaccination programs. With 30% of countries having vaccine coverage below 80%, further delays or disruptions could be catastrophic.
A Call to Action The detection of poliovirus in wastewater in Spain, Germany, and Poland highlights the need for continued vigilance and proactive measures. Public health authorities must leverage wastewater-based surveillance to monitor and respond to potential threats, ensuring that vaccination programs remain robust and effective.
The COVID-19 pandemic has reminded us that viruses know no borders. Ensuring widespread, sustained vaccination is our best defense against polio and other infectious diseases.
For more information on poliovirus and vaccination programs, visit the .
