In the last month there have been warnings about the resurgence of two infectious diseases in Europe – polio and measles. The European Centre for Disease Prevention and Control (ECDC) reported a steep rise in measles cases in 2024. Between February 1st, 2024 and January 31st, 2025, a total of 32,265 people were diagnosed with measles across Europe.
And last week came a combined ECDC and World Health Organisation (WHO) warning about an unusually high number of poliovirus detections in recent months. From September through December 2024, vaccine-derived poliovirus type 2 (VDPV2) was detected in wastewater systems of 14 cities in five European countries – Spain, Poland, Germany, the UK and Finland.
Polio, also known as poliomyelitis, is an extremely contagious disease caused by the poliovirus. It attacks the nervous system and can lead to paralysis within hours. The virus enters through the mouth and multiplies in the intestine. Infected people shed poliovirus into the environment by the faecal-oral route. About one in every 200 infections results in irreversible paralysis, usually affecting the legs.
Most people who get polio do not have any symptoms. Some of those infected will experience symptoms similar to the flu for three to 21 days after infection. These can include: a high temperature, sore throat, headache, tummy pain and aching muscles. These symptoms usually settle within a week.
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In rare cases, more serious symptoms develop, including meningitis and muscle paralysis.
What is the significance of the wastewater detection of the polio virus in European cities? The discovery does not confirm infections in the population, but it is most definitely a wake-up call for Europe, which was declared polio free in 2002. It means that any gaps in vaccination coverage could see a resurgence of the disease.
[ ‘Measles is back’: Cases double in Europe, hitting highest rate in decadesOpens in new window ]
Vaccine-derived polio strains emerge from the weakened live poliovirus contained in oral polio vaccines. If this weakened virus circulates long enough among under-immunised groups or in people with weakened immune systems it can genetically shift back into a form capable of causing disease. According to the ECDC/WHO “genetic sequencing analysis of the European isolates suggests an unusual event in which multiple nearly simultaneous and apparently independent importations likely occurred, from a location outside the catchment areas of European poliovirus surveillance networks.”
The inactivated polio vaccine (IPV), given by injection, cannot revert to a dangerous form. The IPV is free as part of the childhood vaccination programme in Ireland. It’s administered in four doses: at two, four and six months as part of the six-in-one vaccine, and at four to five years as part of the four-in-one vaccine.
Vaccination for polio started in Ireland in 1957. The last recorded case of wild polio here was in 1984, while the infection was eradicated in Europe in 2002.
Because IPV is more expensive and more complex to deliver, oral polio vaccine continues to be used in poorer countries, where it remains effective. But vaccine coverage in parts of the developing world can be as low as 30 per cent as a result of humanitarian crises.
Polio infection can sometimes cause long-term difficulties that require treatment and support. These include: muscle weakness, atrophy (shrinking of the muscles), contractures (tight joints) and deformities, such as twisted feet or legs – conditions that require physiotherapy, occupational therapy and in some cases, surgery. And up to 80 per cent of those infected can redevelop polio symptoms decades after the original infection – a condition called post-polio syndrome.
[ Post-polio syndrome affects 7,000 people who ‘don’t have time to wait’Opens in new window ]
The alert triggered by wastewater surveillance systems in Europe highlights how this form of surveillance can act as a “canary in the coal mine” -providing public health authorities with a useful early warning of infectious disease outbreaks.
But the real key to prevention lies in maintaining sufficiently high levels of immunisation against polio and measles to ensure enough people in our population are vaccinated so that vulnerable groups are protected.
