About 2 - 4 weeks after infection, the person develops a sore called a "mother yaw" where bacteria entered the skin. The sore is a growth that looks like a raspberry. It is usually painless. These sores may last for months. More sores may appear shortly before or after the mother yaw heals.

Other symptoms include:

• Bone pain
• Scarring of the skin
• Swelling of the bones and fingers

In the final stage, sores on the skin and bones can lead to severe disfigurement and disability. This occurs in up to 1 in 5 people who do not get antibiotic treatment.

A sample from a skin sore is examined under a special type of microscope (darkfield examination). There is no blood test for yaws. However, the blood tests for syphilis may be positive in yaws because the two conditions are closely related.