About HIV : How is HIV Disease Transmitted?

A great deal of study has been done on how the virus is transmitted. There are three primary defined modes of transmission:

• Sexually, through intimate contact where body fluids are exchanged;
• Parenterally, through injecting drugs, blood transfusions, or, rarely, needlesticks;
• Perinatally, from an infected mother to her infant, either through birth or breastfeeding.

Scientists have done extensive studies to determine whether the virus can be transmitted in normal social settings. Definitive information shows that this cannot readily occur. Handshakes, toilet seats, doorknobs, etc. will not transmit HIV or AIDS. The only documented cases of transmission outside of the three primary modes have been of health care workers exposed to infected blood or body fluids, and very rarely in household settings. In health care workers, HIV-positive body fluids were either ingested or spilled on skin with cuts or abrasions. Although this risk is very low, it should alert health care workers to the dangers of transmission in the work place, either in the hospital or other health care settings. In the rare documented cases of transmission in household settings, experts believe that infected body fluids came in contact with non-intact skin. It is now evident the risk of transmission of this virus is minimal outside the three major modes described.

Intimate sexual contact is an efficient mode of virus transmission and is the dominant route of epidemic spread. The virus only need come in contact with white blood cells or tissue macrophages which act as both target cells and, subsequently, host cells of the virus. These are primarily CD4+ lymphocytes, monocytes and macrophages. The theory that cuts or abrasions inside body openings are required for transmission to occur is obsolete. We now understand the role that macrophages in mucous membrane linings play in transmission.

The concept of "risk groups" is used mainly for surveillance purposes. Anyone who is uninfected that comes into intimate sexual contact or shares injecting drug paraphernalia with an infected individual may acquire the infection. The virus cannot differentiate between sex, race, age, economic status or even between specific sexual acts. It only needs to come in contact with appropriate white blood cells either in the blood or through mucous surfaces for infection to occur. Researchers also believe that the more virus present, the more likely transmission will occur. As viral burden rises concurrent with disease progression, the potential for transmission increases.

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