Explainer-Why has wild polio been found in Germany and what does it mean?

By Jennifer Rigby

LONDON (Reuters) -Germany has found the wild polio virus in a sewage sample in Hamburg, the first such detection in Europe since 2010. 

WHAT IS POLIO? 

Polio, short for poliomyelitis, is an infectious disease that terrified parents worldwide for much of the first half of the 20th century. Affecting mainly children under five, it is often asymptomatic but can also cause symptoms like fever and vomiting. 

Around one in 200 infections leads to irreversible paralysis, and among those patients, up to 10% die. There is no cure, but it is preventable by vaccination, and case rates globally have reduced by 99% since mass vaccination efforts began in 1988.   

WHAT IS WILD POLIO?

There are two forms of polio: wild polio and vaccine-derived or variant polio. Both can cause paralysis and death, but wild polio is rarer and now only endemic to Afghanistan and Pakistan, causing tens of cases annually. The strain found in German wastewater is linked to the strain circulating in Afghanistan. 

The vaccine-derived form of the virus is more common, although still rare. It causes several hundred cases globally every year, mainly in countries including Yemen and Nigeria. This form of polio stems from the use of an oral polio vaccine containing weakened live virus. 

After children are vaccinated, they shed virus in their faeces for a few weeks. In under-vaccinated communities, this can then spread and mutate back to a harmful version of the virus. A newer version of this vaccine is being rolled out to reduce this risk. 

While countries like Germany no longer use live polio vaccine, others - particularly where polio spreads more commonly - do, as it blocks transmission. 

WHAT DOES DETECTION IN GERMANY MEAN?

Many countries in the world sample sewage to track the spread of polio. Germany's detection is a sign that the system is working well, experts said. There have been no reports of infection in Germany and the risk remains low because vaccination rates are high in the country.  

Detecting wild polio in the region is rare: it has not happened since 2010 in Europe, the WHO said on Wednesday, although that only shows that it has not been detected, rather than that it was not there. 

Other wild polio-free regions have seen more recent detections, or even outbreaks, when the virus was imported to different countries. For example, in 2022 Malawi and Mozambique experienced outbreaks - where there were cases of wild polio in both countries after years without - linked to the strain circulating in Pakistan. 

Detecting the more widespread vaccine-derived polio in otherwise polio-free countries is more common. It has happened several times in Europe and elsewhere in recent years, including the U.S.

WHAT CAN I DO TO PROTECT MYSELF OR MY FAMILY? 

Polio is preventable by either oral or injectable vaccines. Anyone worried about polio should check with their healthcare provider about their vaccination status, or their children's, and make sure they have had the full dose schedule.  

HOW BIG A PROBLEM IS POLIO AND WHAT DOES THIS DETECTION MEAN FOR THE WORLD?

The WHO and other partners, including the Gates Foundation, have been working with governments to end polio for decades. But despite major progress, finishing the job has proved challenging, and expensive. The partnership, called the Global Polio Eradication Initiative, is facing a 30% budget reduction next year amid wider international aid cuts. 

The detection in Germany reiterates the message that polio anywhere is a potential risk everywhere, experts said, and the GPEI said it serves chiefly as a reminder that the world should rally to finish the job of wiping out the disease.

(Reporting by Jennifer Rigby; Editing by Sharon Singleton)