 The purpose of this study is to determine how the body defends itself against Leishmania Viannia, a parasite that can cause a skin infection and skin sores. Certain cells in the immune system act more aggressively against Leishmania in people with mild Leishmania symptoms than in those who have long-term or recurring symptoms of the disease. Participants in the study will include people who currently have Leishmania infection, people who have had the infection in the past, and people who have never been exposed to the parasite. This study will enroll 220 adults, ages 18 to 70 years, at 3 sites in Colombia. Blood samples will be collected from volunteers at least once during the study. Participants will also undergo HIV testing. Volunteers will participate in up to 2 study visits, scheduled 2-3 weeks apart. 