AIDS Continuing Education--NCBTMB Approved

Chapter 1

Modes of Transmission


HIV is transmitted when a bodily fluid containing the virus enters the body; this can be through injection, an open cut or sore, or mucous membrane. Such bodily fluids include blood, menstrual blood, semen, vaginal secretions and breast milk. Fluids which have not been shown to include HIV are saliva, tears, sweat, feces and urine.


3 Most Common Ways to Transfer HIV

  • Contaminated needle
  • Unprotected sex
  • Mother to child

    • Activities which deliver the infected fluid to the body include injection with a needle contaminated with the virus. This can occur through sharing such a needle between users. In the early days of the AIDS crisis, the blood supply for transfusions was not checked. Thus, 90% of hemophiliacs have been infected with HIV. More than ten years ago, steps were taken to protect the blood supply available for transfusions and this is no longer a mechanism of transmission. Health workers can have accidents where they are pricked by a contaminated needle; the rate of infection in this scenario is quite low.


    Unprotected sex is another vehicle of HIV transmission into the body. This can include vaginal and anal sex. The receiving partner in both these situations may incur minute, unnoticed tears in mucous membranes.


    Oral sex (specifically semen coming into contact with the oral cavity) is a less efficient mechanism because the membranes in the mouth are sturdier and the enzymes in saliva make the virus deteriorate. There are no documented instances of the virus entering the body by vaginal oral sex.


    The third main avenue of HIV entering the body is mother to child. Formerly, this often occurred while the baby was in the womb of an infected mother. Between 1992 and 2004 this method declined 95% as mothers tested and sought treatments which reduce the rate of transmission. Infected mothers who do not receive prenatal care are still liable to pass HIV to the unborn child. It is possible to pass the virus to the baby during breast feeding. The United Nations recommends that HIV-infected mothers avoid breast feeding or terminate it as soon as possible.


    There are a number of modalities, in addition to those mentioned above, which do not transmit HIV: insect bites, sharing dishes or food, swimming pools, hot tubs, and pets.



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