HIV infection is the cause of AIDS. The full name of HIV is Human Immunodeficiency Virus. HIV is the virus that attacks the body and causes infection, which eventually develops into AIDS. HIV is mainly found in semen, vaginal secretions, blood, breast milk and other bodily fluids of people with AIDS, so the main ways of transmission of HIV are sexually transmitted, blood-borne, and mother-to-child transmission. After being infected with HIV, the HIV virus attacks the body’s immune cells, mainly CD4+ T lymphocytes. Depending on the symptoms and patient signs after infection, it can be categorized into acute stage, asymptomatic stage and AIDS stage, and AIDS is the final stage after HIV infection i.e. AIDS stage. Before being infected with HIV, individuals should take precautions according to its transmission route. After being infected with HIV, patients should be actively treated so as not to delay their condition.