Smaller numbers of cases are reported from Mauritania, Ethiopia, Chad, Senegal, and Cameroon. Most cases occur in poor rural villages that are not visited by tourists. A few days to hours before the worm emerges, the person might develop a fever and have swelling and pain in the area where the worm is. A blister develops and then opens into a wound. When the wound is immersed in water, the worm begins to emerge.
Most worms appear on the legs and feet, but they can occur anywhere on the body.
After the worm emerges, the wound often becomes painfully swollen and infected. Infected persons usually do not have symptoms until about a year after they drink water contaminated with infected water fleas. Diagnosis is usually made by seeing the adult worm protruding from a skin sore. Anyone who drinks standing pond or well water contaminated by persons with Guinea worm infection is at risk. People who live in villages where the infection is common are at greatest risk.