HIV

Human immunodeficiency virus (HIV) is the virus that causes acquired immune deficiency syndrome (AIDS). HIV weakens a person's immune system leading to life-threatening infections or cancers. A person with HIV is said to have AIDS when they develop such infections or cancers or when their CD4 count drops below 200. CD4 cells are infection fighting white blood cells, also known as T-helper cells, which HIV primarily infects. When CD4 cells drop to this level, a person's ability to fight infection is lost.

HIV infection occurs through the transfer of semen, blood, vaginal fluid, pre-ejaculate, or breast milk. Infection is generally transmitted through unprotected sex, contaminated needles, breast milk, and from an infected mother to her baby at birth. According to the Center for Disease Control and Prevention, the estimated number of people with HIV/AIDS in the United States is about 1.2M with approximately 25% unaware of their infection.

Most HIV infected individuals eventually develop AIDS. Treatment with anti-retrovirals increases the life expectancy of individuals infected with HIV/AIDS. It is hoped that such evolving treatments will allow people with HIV/AIDS to achieve a normal life expectancy.