Poliovirus found in sewage in three European countries. What now?

Health authorities say European countries should ramp up their immunisation and disease surveillance efforts.

Health authorities are sounding the alarm after poliovirus was found in sewage in Germany, Poland, and Spain this autumn.
None of these countries have reported actual cases of poliomyelitis, known also as polio, a highly contagious disease that mostly affects young children and can invade the nervous system and cause paralysis in severe cases.
But local and global health authorities said the recent wastewater detections in Warsaw, Barcelona, Munich, Bonn, Cologne, and Hamburg should serve as a wake-up call for European countries to shore up their disease surveillance programmes and make sure there are no gaps in vaccination that could allow the virus to spread.
While Europe was declared polio-free in 2002, it is still present in other countries, meaning there is always a risk that cases could be imported to European countries and begin to spread among unvaccinated people.
“Anytime that you detect any poliovirus, in any form, from any source, in a previously polio-free area is unusual,” Oliver Rosenbauer, a spokesperson for polio eradication efforts at the World Health Organization (WHO), told Euronews Health.
Poland’s health authorities have warned that kids should get immunised and are updating their stockpile of polio vaccines, while the German health ministry is giving free tests to medical clinics to test for human infections.
In Poland, 85 per cent of one-year-olds were vaccinated against polio last year, which is one of the lowest rates in Europe. That rate was 93 per cent in Spain and 91 per cent in Germany, according to WHO data.
Around 80 per cent of people should be immunised in order to protect the community from infection, health experts say, though Polish authorities said that rate should be 95 per cent among children and adolescents.
But national data can mask gaps at the local level, meaning there may be areas with lower immunisation rates that give the virus an opportunity to take hold.
Across the European Union, as many as 2.4 million children may have gone unvaccinated against polio between 2012 and 2021, according to estimates from the European Centre for Disease Prevention and Control (ECDC).
Travellers from high-risk areas – such as Afghanistan and Pakistan, where polio is still endemic – may also not be fully vaccinated, which could leave them vulnerable if the virus is circulating locally.
“It’s showing that we have pockets [of undervaccinated people] not only outside our doorstep, but within Europe,” Dr Thea K Fischer, a professor at the University of Copenhagen and co-founder of the European Network of Non-polio Enteroviruses, told Euronews Health.
Poliovirus is detected in sewage when people shed traces of the virus in their poop, but it doesn’t necessarily mean that people are sick. It can also be excreted by people who were vaccinated with the oral polio vaccine, which contains a weakened but live virus that prompts an immune response to protect against later infection.
In areas with poor sanitation, the virus can continue to circulate among vulnerable people, and if it spreads for long enough, it can mutate into a stronger strain that causes paralysis.
That isn’t a major concern in countries like Germany, Spain, or Poland, which have robust sanitation and surveillance systems, Rosenbauer said.
Most other European countries also have disease detection programmes that occasionally identify poliovirus in wastewater, such as in the United Kingdom in 2022.
But even countries with wastewater surveillance systems tend to have geographical blindspots that can allow viruses to circulate undetected, Fischer said, and Polish authorities are now expanding their wastewater testing.
“COVID has advanced the rollout and the upscale of the surveillance systems to also cover polio, but it takes time to have a comprehensive environmental system in place,” Fischer said.
The poliovirus samples identified this autumn are type 2, a strain that was declared globally eliminated in 2015 but still appears occasionally in European wastewater from people who were immunised with the oral version of the vaccine, according to a recent study led by Fischer in the journal Lancet Regional Health – Europe.
Its reemergence in recent years underscores the “ongoing threat of cases or outbreaks when imported strains spread in populations with low immunity against locally eliminated strains,” the researchers said.
It’s been a challenging year for the effort to eradicate polio globally.
Pakistan and Afghanistan both launched vaccination campaigns in October amid a resurgence in polio cases this year.
There have been 55 cases in Pakistan and 23 in Afghanistan in 2024, up from six each in 2023.
Gaza also reported its first case in 25 years, after a baby was diagnosed with polio and the virus was detected in the war-torn territory’s sewage over the summer.
That prompted two brief humanitarian pauses in fighting between Israel and Hamas so that the WHO could fully vaccinate nearly 557,000 children under the age of 10.
Health authorities had warned that the virus could spread across borders without a concerted effort to contain it.
“Polio is a highly infectious disease and it spreads mostly silently [over] very long distances,” Rosenbauer said.
“And so we will continue to see [it detected in Europe] until you eradicate the disease completely”.