For 10 points, name this sexually-transmitted infection, a virus that usually leads to AIDS.
This virus uses the proteins gp41 and gp120 to enter cells, and Kaposi's sarcoma, a type of skin cancer, is a sign of its progression. It sharply reduces an infected person's count of CD4+ helper T cells. AZT is shorthand for an anti-retroviral drug treatment of it, and its ongoing pandemic started in 1981. For 10 points, name this sexually-transmitted infection, a virus that usually leads to AIDS.
This virus uses the proteins gp41 and gp120 to enter cells, and Kaposi's sarcoma, a type of skin cancer, is a sign of its progression.
{HIV} or {Human Immunodeficiency Virus}