HIV is the short form for human immunodeficiency virus (HIV). HIV can only be passed from one human to another. It is a virus that attacks and weakens the immune system by destroying CD4 cells. CD4 cells are the cells that help the body fight off infections. With proper treatment and care, people with HIV can live long and healthy lives.

If HIV is not treated, it can progress to AIDS (acquired immunodeficiency syndrome). People are diagnosed with AIDS when the number of CD4 cells is so low that they become sick with infections or cancers that are linked to low immune function. These infections do not usually affect people with healthy immune systems.

Most people with HIV do not show symptoms for several years after infection. This means that they may not know that they have been infected. Even if no symptoms are present, the virus can still be passed to other people. Testing is the only way to know for sure if someone is living with HIV. Testing and treatment are important for preventing long-term harm.