BERLIN, Germany -- The Bill and Melinda Gates Foundation on Sunday pledged to invest $1.2 billion towards wiping out polio as health experts from around the world gathered for a summit in Berlin.

"Polio eradication is within reach. But as far as we have come, the disease remains a threat," Bill Gates, co-chair of the foundation, said in a statement.

The sum will be donated to the Global Polio Eradication Initiative (GPEI), a public-private partnership led by national governments that aims to end the disease by 2026.

Polio is a highly contagious illness caused by a virus that enters the central nervous system and damages cells in the spinal cord and brain.

The disease can be fatal, and those who survive are often left paralysed or with atrophied and twisted limbs.

Polio most often affects children under the age of five but can hit anyone who is not vaccinated.

Since its launch in 1988, the GPEI has helped reduce polio cases by more than 99 percent worldwide and prevented more than 20 million cases of paralysis, the foundation said in a statement.

Pakistan and Afghanistan are the only two countries where the wild poliovirus remains endemic, though Malawi and Mozambique also detected imported wild polio cases in 2022.

"Despite this historic progress, interruptions in routine immunisation, vaccine misinformation, political unrest, and the tragic floods in Pakistan in 2022 have underscored the urgent need to finish the job against polio," the foundation said.

Another concern is that "countries that had previously eliminated all forms of poliovirus have recently reported new detections of the virus", such as Britain and the US, it said.

Partners in the GPEI include the World Health Organization (WHO), Rotary International and the the US Centers for Disease Control and Prevention (CDC).