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The UK has pledged to donate £100m to a global bid to eradicate polio by 2020.

The money will go towards immunising up to 45 million children against polio every year until then, in the hope the world can be declared polio-free.

Polio was wiped out in the UK in the 1980s but is still endemic in Afghanistan and Pakistan.

The highly infectious disease, caused by a virus, mainly affects children under five years old. One in 200 cases lead to irreversible paralysis.

Some children die when the muscles that help them breathe stop working.

The UK funding, which will be administered through the World Health Organization, should help more than 15,000 polio workers reach children still at risk and save 65,000 children from paralysis each year.

The government says the push to end polio was still about £130m short of the £1.1bn global investment needed.

International Development Secretary Priti Patel said the disease had "no place in the 21st Century" and urged other countries to "step up, follow Britain's lead and make polio history".

"The UK has been at the forefront of fighting global health threats, including polio, and our last push towards eradication by 2020 will save 45 million children from contracting this disease.

"The world is closer than it ever has been to eradicating polio for good, but as long as just one case exists in the world, children everywhere are still at risk."

The WHO says polio cases have dropped from an estimated 350,000 in 1998 in more than 125 endemic countries to 37 reported cases in 2016.