Causes of HIV and AIDS

Learn about the human immunodeficiency virus (HIV), which causes acquired immune deficiency syndrome (AIDS). Also find out how HIV is spread.

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What causes HIV infection and AIDS?

HIV infection is caused by a virus. AIDS is a disease that can result from HIV infection.

HIV attacks your body's immune system, making it unable to fight certain illnesses. If you are HIV-positive (infected with HIV):

  • your infection could progress to AIDS if you develop a serious illness, such as pneumonia (a lung infection)
  • you may develop AIDS in 5 to 10 years if you do not get treatment for HIV infection
  • you can live a near-normal lifespan if you start treatment early for HIV infection

How is HIV spread?

HIV is spread by infected body fluids, such as:

  • blood
  • semen
  • fluid from the rectum
  • fluid from the vagina
  • breast milk

HIV can only spread when infected fluid from a person with HIV gets into the bloodstream of another person through:

  • broken skin
  • wet linings of the body, such as the:
    • vagina
    • rectum
    • foreskin
  • the opening of the penis

HIV cannot spread through:

  • healthy, unbroken skin
  • casual contact, such as:
    • hugging
    • kissing
    • shaking hands
  • sharing food
  • mosquito bites
  • toilet seats

If you have HIV, you can pass the virus to your baby during:

  • pregnancy
  • childbirth
  • breastfeeding

You can only spread HIV, not AIDS. That is, whether you have HIV or AIDS, you can only infect others with HIV.

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