What is HIV?
HIV stands for human immunodeficiency virus. It is the virus that causes AIDS. A member of a group of viruses called retroviruses, HIV infects human cells and uses the energy and nutrients provided by those cells to grow and reproduce.
What is AIDS?
AIDS stands for acquired immunodeficiency syndrome. It is a disease in which the body’s immune system breaks down and is unable tot fight off infections, known as “opportunistic infections,” and other illness that take advantage of a weakened immune system. When a person is infected with HIV, the virus enters the body and lives and multiplies primarily in the white blood cells. These are immune cells that normally protect us from disease. The hallmark of HIV infection is the progressive loss of a specific type of immune cell called T-helper, or CD4, cells. As the virus grows, it damages or kills these and other cells, weakening the immune system and leaving the person vulnerable to various opportunistic infections and the illnesses ranging from pneumonia to cancer. A person can receive a clinical diagnosis of AIDS, as defined by the U.S. Centers for Disease Control and Prevention (CDC), if he or she has tested positive for HIV and meets one of both of these conditions:
- The presence of one or more AIDS-related infections or illnesses
- A CD4 count that has reached or fallen below 200 cells per cubic millimeter of blood. Also called the T-cell count, the CD4 count ranges from 450 to 1200 in healthy individuals.
How is HIV transmitted?
A person who has HIV carries the virus in certain bodily fluids, including blood, semen, vaginal secretions, and breast milk. The virus can be transmitted only if such HIV-infected fluids enter the bloodstream of another person. The kind of direct entry can occur:
- through the linings of the vagina, rectum, mouth, and the opening at the top of the penis;
- through intravenous injection with a syringe; or
- through a break in the skin, such as a cut or sore.
Usually, HIV is transmitted through:
- Unprotected sexual intercourse (either vaginal or anal) with someone who has HIV
Women are at a greater risk of HIV infection through vaginal sex than men, although the virus can also be transmitted from women to men. Anal sex (whether male-male or male-female) poses a high risk mainly to the receptive partner, because the lining of the anus and rectum is extremely thin and is filled with small blood vessels that can be easily injured during intercourse.
- Unprotected oral sex with someone who has HIV
There are far fewer cases of HIV transmission attributed to oral than to either vaginal or anal intercourse, but oral-genital contact poses a clear risk of HIV infection, particularly when ejaculation occurs in the mouth. This risk goes up when either partner has cuts or sores, such as those caused by sexually transmitted infections (STIs), recent tooth brushing, or canker sores, which can allow the virus to enter the bloodstream.
- Sharing needles or syringes with someone who is HIV infected
Laboratory studies show that infections HIV can survive in used syringes for a month or more. That’s why people who inject drugs should never reuse or share syringes, water, or drug preparation equipment. This includes needles or syringes used to inject illegal drugs such as heroin, as well as steroids. Other types of needles, such as those used for body piercing and tattoos, can also carry HIV.
- Infection during pregnancy, childbirth, or breastfeeding (mother-to-infant transmission)
Any woman who is pregnant or considering becoming pregnant and thinks she may have been exposed to HIV–even if the exposure occurred years ago–should seek testing and counseling. In the U.S., mother-to-infant transmission has dropped to just a few cases each year because pregnant women are routinely tested for HIV. Those who test positive can get drugs to prevent HIV from being passed on to a fetus or infant, and they are counseled not to breastfeed.
How is HIV not transmitted?
HIV is not an easy virus to pass from one person to another. It is not transmitted through food or air (for instance, by coughing or sneezing). There has never been a case where a person was infected by ya household member, relative, coworker, or friend through casual or everyday contact such as sharing eating utensils or bathroom facilities, or through hugging or kissing. (Most scientists agree that while HIV transmission through deep or prolonged “French” kissing may be possible, it would be extremely unlikely) Here in the U.S. screening the blood supply for HIV has virtually eliminated the risk of infection through blood transfusions (and you cannot get HIV from giving blood at a blood bank or other established blood collection center). Sweat, tears, vomit, feces, and urine do contain HIV, but have not been reported to transmit the disease (apart from two cases involving transmission from fecal matter to cut skin). Mosquitoes, fleas, and other insects do not transmit HIV.