Polio: what is it and what are the symptoms?

Traces of polio have been found in a London sewage works.

It is a rare but serious infection caused by a virus that spreads when an infected person coughs or sneezes, or through food, water or objects that have been in contact with their faeces.

Thanks to high levels of vaccination, the virus has largely been eliminated across the globe.

The NHS says that most people who get polio do not experience symptoms, but some may experience mild flu-like symptoms.

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