Acquired immune deficiency syndrome fatal transmissible disease of the immune system caused by the human immune deficiency virus ( HIV), HIV slowly attacks and destroys the immune system, the body’s defense against infection, leaving an individual vulnerable to a variety of other infections and certain malignancies that eventually causes death. AIDS is the final stage of HIV infection.

Diagnosis, treatment and prevention

Tests for the disease check for antibodies to HIV, which appear from four weeks to six months after exposure. The most common test for HIV is the Enzyme- linked Immuno Sorbent Assay (ELISA). If the result is positive, the test is repeated on the same blood sample. Another positive result is confirmed using  a more specific test such as the Western blot. A problem with ELISA is that it produces false positive results in people who have been exposed to parasitic diseases such as malaria; this is particularly troublesome in Africa, where both AIDS and malaria are rampant. Polymerase chain reaction (PCR) tests, which screen for viral RNA and therefore allow detection of the virus after very recent exposure, and Single Use Diagnostic Screening (SUDS) are other options. Because these tests are very expensive, they are often out of reach for the majority of the population at risk for the disease. Pharmaceutical companies are developing new tests that are less expensive and that do not need refrigeration, allowing for a greater testing of the at-risk population around the world.

There is no cure or effective vaccine for HIV infection. Efforts at prevention have focused primarily on changes in sexual behavior such behavior such as the practice of abstinence and the use of condoms. Attempts to reduce intravenous drug use and to discourage the sharing of needles have also led to a reduction in infection rates in some areas. HIV infection is treated with three classes of antiretroviral medications, Protease inhibitors, which inhibit the action of an HIV enzyme called protease, include ritonavir, saquiniver, indinavir, amprenivir, nelfinavir and lopinavir. Nucleoside reverse transcriptase (RT) inhibitors (e.g., abacavir [ABC], zidovudine [AZT], zalcitabine [ddC], didanosine [ddI], stavudine [d4T] and lamivudine [3TC]) and lamivudine [3TC] and non-nucleoside RT inhibitors (e.g., efavirenz, delavirdine, and nevirapine) both inhibit the action of reverse transcriptase, Each drug has unique side effects, and in addition, treatment with combinations of these drugs leads to additional side effects including a fat-redistribution condition called lipodystrophy.

Because HIV reapidly become resistant to any single antiretroviral drug, combination treatment is necessary for effective suppression of the virus. Highly active antiretroviral therapy (HAART), a combination of three or more RT and protease inhibitors, has resulted in a marked drop in the mortality rate from HIV infection in the United States and other industrialized states since its introduction in 1996. Because of its high cost. HAART is generally not available in regions of the world hit hardest by the AIDS epidemic. Although HAART does not appear to eradicate HIV, it largely halts viral replication, thereby allowing the immune system to reconstiture itself. Levels of free virus in the blood become undetectable; however, the virus is still present in reservoirs, the best-known of which is a latent reservoir in a subset of helper T cells called resting memory T cells. The virus can persist in a laten state in these cells, which have a long life span due to their role in allowing the immune system to respond readily to previously encountered infections. These latently infected cells represent a major barrier to curing the infection. Patients successfully treated with HAART no longer suffer from the AIDS-associated conditions mentioned above, although severe side effects may accompany the treatment. Patients must continue to take all of the droups without missing does in the prescribed combination or risk developing a drug-resistant virus; viral replication resumes if HAART is discontinued.