Infection with human immunodeficiency virus (HIV) causes acquired immunodeficiency syndrome (AIDS) due to the destruction of the immune system. According to the Centers for Disease Control and Prevention (CDC), HIV has caused 35,962 cases of AIDS in the United States as of 2007. Three factors must exist for HIV to spread, as reported by the San Francisco AIDS Foundation: HIV must be present; it must be present in sufficient quantity; and it must get into the blood stream. There are a few different routes of transmission that satisfy these three factors, which may result in the spreading of the virus.
Unprotected Sex
AVERT, an international AIDS and HIV charity based in the UK, states that one of the main routes of HIV transmission includes unprotected penetrative sex whereby one of the partners is infected with the virus. "Unprotected" refers to sexual activity without a condom, which provides a physical barrier between sexual partners. "Penetrative" refers to vaginal or anal sexual activity. According to the San Francisco AIDS Foundation, the person being penetrated, whether anally or vaginally, is more at risk of being infected than the male performing the penetration because the virus is present in sufficient amounts for transmission in the semen, and because the anal and vaginal tissues are subject to tearing during penetration.
Contaminated Needles
Transmission through contaminated needles is another main route of infection with HIV. The CDC describes how health care workers have been infected with HIV by accidentally sticking themselves with needles used to draw blood or inject medications into infected persons. Another way that contaminated needles can result in the transmission of HIV is through sharing needles for drug injection. This can occur through the injection of illegal drugs, such as heroine, or legal drugs, such as insulin. Because sharing needles with an infected person involves injecting a drug directly into one's own blood stream with a needle contaminated with blood carrying the virus, this is a very efficient route of transmission.
Mother to Child
Babies born to mothers who are infected with HIV can also become infected with the virus. The CDC describes that this type of transmission occurs before or during the birthing process, or after birth when babies breastfeed. The San Francisco AIDS Foundation adds that there were only 48 babies infected with HIV by their mothers in 2004, down from 952 babies in 1992, due to treatment received and precautions taken by the mothers.
Other blood products
Because certain bodily fluids of an infected person, such as blood and semen, carry enough of the virus to infect another person, procedures that involve contact between these bodily fluids can theoretically result in transmission of the virus. According to the San Francisco AIDS foundation some of these methods of transmission include the transference of a product called Factor IV that is pooled from the blood of many different donors to treat hemophilia, blood transfusions, and insemination with an anonymous donor. However, donor blood and semen are all now screened for HIV, and are not used if the blood is infected. Factor IV is now subjected to high heat before transfer to kill any virus present. Since these protective measures have been enacted, transmission through these methods has virtually disappeared.
