Guinea Worm Disease is a tropical disease caused by drinking unfiltered water in Africa. In 1986 3,500.000 people were affected by it. In 2022, a total of 13 people in the entire world are known to have been affected by it. This is due to the work of organizations such as The Carter Center, and others. For more information see:
https://www.cdc.gov/parasites/guineaworm/index.html
NOTE: Currently The Carter Center is working on River Blindness.