HIV originated from SIV in primates and was transferred to humans through zoonosis. In the 1980s, AIDS claimed 14 million lives. AIDS is caused by HIV which attacks immune cells, killing them and causing a disorder rather than a disease. HIV is transmitted through unprotected sex, blood exposure, or from mother to child during birth or breastfeeding. Prevention focuses on stopping HIV transmission through safe sex practices, clean syringes, and blood screening to avoid discrimination and stigma against those infected.