HIV/AIDS

Some important facts about the evidence that HIV causes AIDS are:

• Tests for HIV antibody in persons with AIDS show that they are infected with the virus.
• HIV has been isolated from persons with AIDS and grown in pure culture.
• Studies of blood transfusion recipients before 1985 documented the transmission of HIV to previously uninfected persons who subsequently developed AIDS.

Before the discovery of human immunodeficiency virus (HIV), the virus that causes AIDS, epidemiologic studies of AIDS patients' sex partners and AIDS cases occurring in blood transfusion recipients before 1985 clearly showed that the underlying cause of AIDS was an infectious agent. Infection with HIV has been the only common factor shared by persons with AIDS throughout the world, including homosexual men, transfusion recipients, persons with hemophilia, sex partners of infected persons, children born to infected women, and health care workers who were infected with HIV while on the job, mainly by being stuck with a needle used on an HIV-infected patient.

Although we know that HIV is the cause of AIDS, much remains to be known about exactly how HIV causes the immune system to break down. Scientists are constantly discovering more information about HIV and AIDS. These discoveries help people learn how to stop transmission of the virus and help people infected with HIV to live longer, healthier lives. One important question to answer is why some people exposed to HIV become infected and others do not. Scientists believe it is most likely because of how infectious the other person is and how they are exposed. For example, more than 90 percent of persons who were exposed through an HIV-infected unit of blood became infected. So we know that blood-to-blood contact is a very efficient way that HIV is spread. On the other hand, many health care workers are splashed with blood or bloody body fluids and this type of exposure has caused very few occurrences of HIV infection. Researchers know how HIV is spread and the ways that people can help protect themselves from being exposed to HIV.