Acquired immune deficiency syndrome

Acquired immune deficiency syndrome


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 cells are also called "T-cells" or "helper cells"; they are a type of immune cell. AIDS is also defined by numerous opportunistic infections and cancers that occur in the presence of HIV infection.

Alternative Names

Acquired immune deficiency syndrome


AIDS is the fifth leading cause of death among persons between ages 25 and 44 in the United States, down from number one in 1995. About 25 million people worldwide have died from this infection since the start of the epidemic, and 40.3 million people are currently living with HIV/AIDS globally

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 healthy immune systems can cause fatal illnesses in people with AIDS.

HIV has been found in saliva, tears, nervous system tissue and spinal fluid, blood, semen (including pre-seminal fluid), vaginal fluid, and breast milk. However, only blood, semen, vaginal secretions, and breast milk generally transmit infection to others.

Transmission of the virus occurs:

  • Through sexual contact -- including oral, vaginal, and anal sex
  • Through blood -- via blood transfusions (now extremely rare in the U.S) or needle sharing
  • From mother to child -- a pregnant woman can transmit the virus to her fetus through their shared blood circulation, or a nursing mother can transmit it to her baby in her milk

Other transmission methods are rare and include accidental needle injury, artificial insemination with donated semen, and organ transplants.

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
  • 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 who don't receive HIV therapy during pregnancy
  • People who received blood transfusions or clotting products between 1977 and 1985 (prior to the beginning 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 (defined as 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 that prevents the virus from attaching to certain immune receptors.


The symptoms of AIDS are primarily the result of infections that do not normally develop in individuals with healthy immune systems. These are called opportunistic infections.

Patients with AIDS have had their immune system depleted by HIV and are very susceptible to such opportunistic infections. Common symptoms are fevers, sweats (particularly at night), swollen glands, chills, weakness, and weight loss.

See the signs and tests section below for a list of common opportunistic infections and major symptoms associated with them.

Note: Initial infection with HIV can produce no symptoms. Most people, however, do experience flu-like symptoms with fever, rash, sore throat, and swollen lymph nodes, usually two weeks after contracting the virus. Some people with HIV infection remain without symptoms for years between the time of exposure and development of AIDS.

Exams and Tests

The following is a list of AIDS-related infections and cancers that people with AIDS acquire as their CD4 count decreases. Previously, having AIDS was defined as having HIV infection and getting one of these additional diseases. Now it is additionally defined as a CD4 count below 200, even without an opportunistic infection. Many other illnesses and corresponding symptoms may develop in addition to those listed here.

Common with CD4 count below 350 cells/ml:

  • Herpes simplex virus -- causes ulcers/vesicles in the mouth or genitals, occurring more frequently and more severely in an HIV-infected patient than before HIV infection
  • Tuberculosis -- infection by the tuberculosis bacteria that predominately affects the lungs, but can affect other organs such as the bowel, lining of the heart or lungs, brain, or lining of the central nervous system
  • Oral or vaginal thrush -- yeast infection of the mouth or genitals
  • Herpes zoster (Shingles) -- ulcers/vesicles over a discrete patch of skin caused by the varicella zoster virus
  • Non-Hodgkin's lymphoma -- cancer of the lymph glands
  • Kaposi's sarcoma -- Cancer of the skin, lungs, and bowel, associated with a herpes virus (HHV-8). Can occur at any CD4 count, but more likely at lower CD4 counts, and more common in men than women

CD4 count below 200 cells/ml

  • Pneumocystis carinii pneumonia, "PCP pneumonia," now called Pneumocystic jiroveci pneumonia
  • Candida esophagitis -- painful yeast infection of the esophagus
  • Bacillary angiomatosis -- Skin lesions caused by a bacteria called Bartonella, which is usually acquired from cat scratches

CD4 count below 100 cells/ml

  • Cryptococcal meningitis -- infection of the lining of the brain by a yeast
  • AIDS dementia -- worsening and slowing of mental function, caused by HIV itself
  • Toxoplasmosis encephalitis -- infection of the brain by a parasite, which is frequently found in cat feces; causes discrete lesions in the brain
  • Progressive multifocal leukoencephalopathy -- a viral disease of the brain caused by a virus (called the JC virus) that results in a severe decline in cognitive and motor functions
  • Wasting syndrome -- extreme weight loss and loss of appetite, caused by HIV
  • Cryptosporidium diarrhea -- Extreme diarrhea caused by one of several related parasites

CD4 count below 50/ml

  • Mycobacterium avium -- a blood infection by a bacterium related to tuberculosis
  • Cytomegalovirus infection -- a viral infection that can affect almost any organ system, especially the large bowel and the eyes

In addition to the CD4 count, HIV RNA load, and basic screening lab tests, regular vaginal Pap smears are important to monitor in HIV infection, due to the increased risk of cervical cancer in immunocompromised patients. . Anal Pap smears to detect potential cancers may also be important in both HIV infected men and women.


There is no cure for AIDS at this time. However, a variety of treatments are available that can delay the progression of disease for many years, and improve the quality of life of those who have developed symptoms.

Antiretroviral therapy suppresses the replication of the HIV virus in the body. A combination of several antiretroviral agents, termed highly active antiretroviral therapy (HAART), has been highly effective in reducing the number of HIV particles in the blood stream, as measured by a blood test called the viral load. This can help the immune system recover from the HIV infection and improve T-cell counts.

Although not a cure for HIV, and people on HAART with suppressed levels of HIV can still transmit the virus to others through sex or sharing of needles, these treatments have been enormously effective for the past ten years. There is good evidence that if the levels of HIV remain suppressed and the CD4 count remains high (above 200), life can be significantly prolonged and improved. However, HIV may become resistant to HAART in patients who do not take their medications on schedule every day. Genetic tests are now available to determine whether a particular strain is resistant to a particular drug -- these may be useful in determining the best drug combination, and adjusting the regimen if it starts to fail. These tests should be performed for any failing treatment course, and prior to starting therapy.

When HIV becomes resistant to HAART, salvage therapy is required, to try to suppress the resistant strain of HIV. Different combinations of medications are used to try to reduce viral load, and there are a variety of new drugs coming out on the market for the treatment of drug-resistant HIV.

Treatment with HAART is not without complications. HAART is a collection of different medications, each with its own side effects. Some common side effects are nausea, headache, weakness, malaise, and fat accumulation on the back and abdomen ("buffalo hump"). When used long-term, these medications increase the risk of heart attack by affecting fat breakdown, specifically through increasing lipids and glucose levels.

Any doctor prescribing HAART should carefully follow the patient for possible side effects associated with the combination of medications the patient takes. In addition, routine blood tests measuring CD4 counts and HIV viral load (a blood test that measures how much virus is in the blood) should be taken every three to four months. The goal is to get the CD4 count as close to normal as possible, and to suppress the HIV viral load to an undetectable level.

Other antiviral agents are in investigational stages and many new drugs are in development. In addition, growth factors that stimulate cell growth, such as Epogen (erthythropoetin) and G-CSF are sometimes used to treat anemia and low white blood cell counts associated with AIDS.

Medications are also used to prevent opportunistic infections (such as Pneumocystis carinii pneumonia

Support Groups

Joining support groups where members share common experiences and problems can often help the emotional stress of devastating illnesses. See AIDS - support group.

Outlook (Prognosis)

At the present time, there is no cure for AIDS. It is always fatal if no treatment is provided. In the U.S., most patients survive many years following diagnosis because of the availability of HAART. HAART has dramatically increased the time from diagnosis to death, and research continues in the areas of drug treatments and vaccine development. Unfortunately, HIV medications are not always available in the developing world, where the bulk of the epidemic is raging, due to socioeconomic reasons.

Possible Complications

When a person is infected with HIV, the virus slowly begins to destroy that person's immune system. How fast this occurs differs in each individual. Treatment with HAART can help slow and even halt the destruction of the immune system.

Once the immune system is severely damaged, that person has AIDS, and is now susceptible to infections and cancers that most healthy adults would not get. However, antiretroviral treatment can still be very effective, even at that stage of illness.

When to Contact a Medical Professional

Call for an appointment with your health care provider if you have any of the risk factors for HIV infection, or if symptoms of AIDS are present. By law, AIDS testing must be kept confidential. Your health care provider will review results of your testing with you.


  1. See the article on safe sex to learn how to reduce the chance of acquiring or spreading HIV, and other sexually transmitted diseases.
  2. Try not to use intravenous drugs. If IV drugs are used, do not share needles or syringes. Many communities now have needle exchange programs, where used syringes can be disposed of and new, sterile needles obtained for free. These programs can also provide referrals to addiction treatment.
  3. Avoid contact with another person's blood when the HIV status of the bleeding individual is unknown. Protective clothing, masks, and goggles may be appropriate when caring for people who are injured.
  4. Anyone who tests positive for HIV can pass the disease to others and should not donate blood, plasma, body organs, or sperm. An infected person should warn any prospective sexual partner of their HIV-positive status, should not exchange body fluids during sexual activity, and should use whatever preventive measures (such as condoms) will afford the partner the most protection.
  5. HIV-positive women who wish to become pregnant should seek counseling about the risk to unborn children, and medical advances which may help prevent the fetus from becoming infected. Use of certain medications can dramatically reduce the chances that the baby will become infected during pregnancy.
  6. Mothers who are HIV-positive should not breast feed their babies.
  7. Safe-sex practices, such as latex condoms, are highly effective in preventing HIV transmission. HOWEVER, there remains a risk of acquiring the infection even with the use of condoms, if the condom breaks. Abstinence is the only sure way to prevent sexual transmission of HIV.

The riskiest sexual behavior is unprotected receptive anal intercourse -- the least risky sexual behavior is receiving oral sex. Performing oral sex on a man is associated with some risk of HIV transmission, but this is less risky than unprotected vaginal intercourse. Female-to-male transmission of the virus is much less likely than male-to-female transmission. Performing oral sex on a woman who does not have her period carries low risk of transmission.

HIV-positive patients who are taking anti-retroviral medications are less likely to transmit the virus. For example, pregnant women who are on effective treatment at the time of delivery with undetectable viral loads transmit HIV to the infant <1% of the time, compared to approximately 20% if medications are not used.

The U.S. blood supply is among the safest in the world. Nearly all people infected with HIV through blood transfusions received those transfusions before 1985, the year HIV testing began for all donated blood. Currently, the risk of infection with HIV through a blood transfusion or blood products is vanishingly low in the United States, even in geographic areas with high HIV prevalence.

If you believe you have been exposed to HIV, seek medical attention IMMEDIATELY. There is some evidence that an immediate course of antiviral drugs can reduce the chances that you will be infected. This is called post-exposure prophylaxis (PEP), and has been used to treat health care workers injured by needlesticks, to prevent ultimate transmission.

There is less information on the effectiveness of PEP for people exposed via sexual activity or intravenous drug use. However, if you believe you have been exposed, you should discuss the possibility with a knowledgeable specialist (check local AIDS organizations for the latest information) as soon as possible. Anyone who has been raped should be offered PEP and should consider its potential risks and benefits in their particular case.

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