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How is HIV transmitted?

HIV is transmitted when infected blood, semen, vaginal fluids or breast milk enter another person's body. This most often occurs during unprotected sex or during injection drug use (when needles or other drug paraphernalia are shared).

HIV is spread in the following ways:

Unprotected sexual intercourse
HIV can enter the body during sex through the mucous membranes of the anus, vagina, penis (urethra) or mouth and through cuts, sores and abrasions on the skin. Unprotected anal and vaginal sex are the riskiest sexual activities. There are a small, but growing, number of reported cases of HIV transmission through oral sex; however, the risk of oral sex transmission is clearly lower than for anal or vaginal sex.

Injection drug use
Using shared, unsterile needles and syringes carries a high risk of HIV transmission. Sharing cookers, cottons and water for mixing/bleaching can also transmit HIV.

From an infected mother to her infant
HIV can be transmitted from mother to child during pregnancy, during birth or through breast-feeding. However, with effective treatment of HIV the risk of transmission from mother to child is greatly reduced. Consequently, all pregnant women should see their doctor, be tested for HIV and obtain recommended treatment.

HIV is rarely transmitted in the following ways:

Blood transfusions and organ transplants
The risk of acquiring HIV from a blood transfusion or organ transplantation today is estimated to be about 1 in every 600,000 transfusions. Blood and organ banks do extensive testing on specimens of blood, blood products and organs for HIV and other blood-borne germs.

The health care setting
There is a very small, but real, risk of health care workers getting HIV from patients as a result of needle stick accidents and other substantial blood exposures. The risk of patients getting infected from health care workers is also very small.

HIV is not  transmitted by:

Casual contact
HIV is not spread by casual contact. It dies quickly outside the body and is easily killed by soap and by common disinfectants such as bleach. There is no risk of HIV infection from: 

  • donating blood 
  • mosquito bites 
  • toilet seats 
  • shaking hands 
  • hugging 
  • sharing eating utensils 
  • food or objects handled by people with HIV or AIDS 
  • spending time in the same house, business, or public place with a person with HIV/AIDS

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Information courtesy Public Health – Seattle & King County.