Nicknamed the new AIDS of the Americas, chagas is a tropical disease caused by parasites transmitted to humans by blood-sucking insects. The insect, called kissing bug, bites people in order to ingest human blood, while it excretes the parasite at the same time. When the victim scratches the itch, the parasite moves into the wound to infect the person.

Medically known as American trypanosomiasis, chagas kills about 20,000 people each year and is hard or impossible to cure. The disease can be transmitted from mother to child or by blood transfusion. About a quarter of its victims eventually develop enlarged hearts or intestines, which can fail or burst, causing sudden death. Treatment involves harsh drugs taken for up to three months and works only if the disease is caught early.

Unlike HIV, chagas is not a sexually-transmitted disease, but it does exhibit some similarities to HIV in that it's also a chronic disease requiring prolonged, expensive treatment.