What is HIV?

HIV (human immunodeficiency virus) is the virus that causes AIDS (acquired immunodeficiency syndrome). By killing or damaging cells of the body's immune system, HIV progressively destroys the body's ability to fight infections and certain cancers. People diagnosed with AIDS may get life-threatening diseases called opportunistic infections, which are caused by microbes such as viruses or bacteria that usually do not make healthy people sick.

How is HIV transmitted?

HIV is spread most commonly in these ways:

  • By having unprotected sex with an infected partner. The virus can enter the body through the lining of the rectum, vagina, vulva, penis, or mouth during sex. Having a sexually transmitted disease such as syphilis, genetal herpes, chlamydia, gonorrhoea, bacterial vaginosis or trichomoniasis makes people more susceptible to acquiring HIV infection during sex with infected partners.
  • Through contact with infected blood. Before blood was screened for HIV infection and before techniques were introduced to destroy HIV in blood products, HIV was sometimes transmitted through transfusions of contaminated blood or blood products. Today, because of blood screening and heat treatment of blood derivatives, the risk of getting HIV from blood products in Australia is extremely small.
  • By sharing needles or syringes (such as during drug use), the virus can be transmitted from the very small amount of blood remaining on the needle. Uncommonly, HIV is transmitted to health care workers or others from needle-stick injuries or other infected medical instruments.
  • To the newborn during pregnancy or birth. Approximately one-quarter to one-third of all untreated pregnant women infected with HIV will pass the infection to their babies. HIV also can be spread to babies through the breast milk of mothers infected with the virus. However, with appropriate treatment of the mother during pregnancy and the baby after birth, the risk of the newborn becoming infected is very small.
  • It is important to know HIV cannot be transmitted by mosquito or other insect bites. It cannot be spread by contact with tear, sweat or saliva (being spit on) or through physical contact such as hugging, holding hands, closed mouth kissing, using the same toilet or sharing  utensils. It is also extremely unlikely for HIV to be transmitted via open-mouth kissing although this is theoretically possible if there are open sores or blood is present. 

Last Review Date: April 18, 2012