AIDS (acquired immunodeficiency syndrome) / HIV (human immunodeficiency virus)
AIDS is a chronic, life-threatening condition caused by the human immunodeficiency virus (HIV). By damaging or destroying the cells of your immune system, HIV interferes with your body's ability to effectively fight off viruses, bacteria and fungi that cause disease. This makes you more susceptible to opportunistic infections your body would normally resist, such as pneumonia and meningitis, and to certain types of cancers.
The virus and the infection itself are known as HIV. The term AIDS (acquired immunodeficiency syndrome) is used to mean the later stages of HIV infection. But both the terms HIV and AIDS refer to the same disease.
HIV is most commonly spread by sexual contact with an infected partner. It can also spread through infected blood and shared needles or syringes contaminated with the virus. Untreated women with HIV also can pass the infection to their babies during pregnancy, delivery or through their breast milk.
In the two decades since the first reports of the disease, AIDS has become a global epidemic. Worldwide, an estimated 40 million people are living with HIV, including an estimated 2.5 million children younger than 15. According to the United Nations Program on HIV/AIDS (UNAIDS) and the World Health Organization (WHO) , 5 million people were newly infected with HIV in 2003 and 3 million people died from AIDS.
In sub-Saharan Africa, the area of the world most severely impacted by AIDS, 3 million new infections occurred in 2003, and there were 2.3 million AIDS deaths. The AIDS epidemic is also growing fast in China, India, Indonesia, Russia, Eastern Europe and Central Asia.
Currently, an estimated 850,000 to 950,000 Americans are living with HIV/AIDS. This is partly the result of improved treatments. Since 1995 the number of medications available to treat AIDS has greatly increased, and powerful combinations of newer antiretroviral drugs have helped reduce serious complications of the disease and prolong life. But the emergence of drug-resistant forms of HIV threatens the positive news about treatment.
Of equal concern is a growing public complacency about AIDS. Nearly a third of the people living with HIV don't know they're infected and so are more likely to spread the disease. And reports from several cities in both the United States and Europe show increased high-risk behavior among young gay men. Drug use is also fueling the spread of HIV here and abroad. These facts have led experts to warn that the 20-year-old epidemic is still in its early stages.
AIDS (Acquired Immune Deficiency Syndrome) is the final and most serious stage of HIV disease, which causes severe damage to the immune system.
According to the Centers for Disease Control and Prevention, AIDS begins when a person with HIV infection has a CD4 cell count below 200. (CD4 is also called "T-cell", a type of immune cell.) AIDS is also defined by numerous opportunistic infections and cancers that occur in the presence of HIV infection.
Causes, incidence, and risk factors
About 47 million people worldwide have been infected with HIV since the start of the epidemic.
Human immunodeficiency virus (HIV) causes AIDS. The virus attacks the immune system and leaves the body vulnerable to a variety of life-threatening infections and cancers.
Common bacteria, yeast, parasites, and viruses that ordinarily do not cause serious disease in people with fully functional immune systems can cause fatal illnesses in people with AIDS.
HIV has been found in saliva, tears, nervous system tissue, blood, semen (including pre-seminal fluid), vaginal fluid, and breast milk. However, only blood, semen, vaginal secretions, and breast milk have been proven to transmit infection to others.
Transmission of the virus occurs:
Other transmission methods are rare and include accidental needle injury, artificial insemination with donated semen, and through a donated organ.
HIV infection is not spread by casual contact such as hugging, by touching items previously touched by a person infected with the virus, during participation in sports, or by mosquitoes.
It is not transmitted to a person who DONATES blood or organs. Those who donate organs are not in direct contact with those who receive them. Likewise, a person who donates blood is not in contact with the person receiving it. In all these procedures, sterile needles and instruments are used.
However, HIV can be transmitted to a person RECEIVING blood or organs from an infected donor. This is why blood banks and organ donor programs screen donors, blood, and tissues thoroughly.
Those at highest risk include persons engaging in unprotected sex, the sexual partners of those who participate in high-risk activities (such as anal sex), intravenous drug users who share needles, infants born to mothers with HIV, and people who received blood transfusions or clotting products between 1977 and 1985 (prior to standard screening for the virus in the blood).
AIDS begins with HIV infection. People infected with HIV may have no symptoms for ten years or longer, but they can still transmit the infection to others during this symptom-free period. Meanwhile, if the infection is not detected and treated, the immune system gradually weakens and AIDS develops.
Acute HIV infection progresses over time to asymptomatic HIV infection and then to early symptomatic HIV infection. Later, it progresses to AIDS (very advanced HIV infection with T-cell count below 200).
Most individuals infected with HIV, if not treated, will develop AIDS. There is a small group of patients who develop AIDS very slowly, or never at all. These patients are called non-progressors and many seem to have a genetic difference which prevents the virus from attaching to certain immune receptors.
If you're infected with HIV, you're also more likely to develop certain cancers, especially Kaposi's sarcoma, cervical cancer and lymphoma.