HIV-1 is a type of human immunodeficiency virus that primarily causes AIDS (acquired immunodeficiency syndrome). It attacks the body's immune system, specifically targeting CD4 cells, which are crucial for fighting infections. Without treatment, HIV-1 can lead to severe immune system damage and increase the risk of opportunistic infections and certain cancers. The virus is transmitted through contact with infected bodily fluids, such as blood, semen, vaginal fluids, and breast milk. Effective treatments, known as antiretroviral therapy (ART), can help manage the virus, allowing individuals to live longer, healthier lives and reducing the risk of transmission to others.