Participants undergo a complete medical history and physical examination, blood tests, electrocardiogram (EKG), ultrasound tests of the heart and abdomen, and a 6-minute walk (distance test) to determine exercise capacity. Blood tests include screening for HIV, hepatitis B and C, schistosomiasis, hookworm and malaria. Patients who test positive for HIV, hepatitis B or C, schistosomiasis, hookworm or malaria are referred for treatment at Ahmadu Bello University Teaching Hospital in Zaria, Nigeria, and those who test negative for hepatitis B are referred for vaccination. Genetic tests focus on genes involved in SCD, PHTN, inflammation, blood vessel function and red blood cell function.