Scientists are calling for urgent action on free-living amoebas – a little-known group of microbes that could pose a growing global health threat. Here’s what you need to know.

Free-living amoebas are single-celled organisms that don’t need a host to live. They are found in soil and water, from puddles to lakes.

What makes them remarkable is their ability to change shape and move using temporary arm-like extensions called pseudopodia – literally “false feet”. This allows them to thrive in an astonishing range of environments.

The most notorious free-living amoeba is Naegleria fowleri, commonly known as the “brain-eating amoeba”. It lives naturally in warm freshwater, typically between 30°C and 40°C – lakes, rivers and hot springs. But it is rarely found in temperate countries such as the UK, due to the cold weather.

The infection happens when contaminated water enters through the nose, usually while swimming. From there, the amoeba travels along the nasal passages to the brain, where it destroys brain tissue. The outcome is usually devastating, with a mortality rate of 95%-99%.

Occasionally, Naegleria fowleri has been found in tap water, particularly when it’s warm and hasn’t been properly chlorinated. Some people have become infected while using contaminated tap water to rinse their sinuses for religious or health reasons.

Fortunately, you cannot get infected by drinking contaminated water, and the infection doesn’t spread from person to person.

Brain-eating amoebas can be killed by proper water treatment and chlorination. But........

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