Causes: 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, which is the liquid that comes out before

ejaculation), vaginal fluid, and breast milk. However, only blood, semen, vaginal secretions, and breast milk generally transmit infection to others.

The virus can be spread (transmitted):

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 breast milk.

Other methods of spreading the virus are rare and include accidental needle injury, artificial insemination with infected donated semen, and organ transplantation with infected organs.

HIV infection is NOT spread by: Casual contact such as hugging, Mosquitoes, Participation in sports and Touching items previously touched by a person infected with the virus.

AIDS and blood or organ donation:

AIDS is NOT transmitted to a person who DONATES blood or organs. Those who donate organs are never 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. To reduce this risk, blood banks and organ donor programs screen donors, blood, and tissues thoroughly.

People at highest risk for getting HIV include: Injection drug users who share needles, Infants born to mothers with HIV who didn't receive HIV therapy during pregnancy, People engaging in unprotected sex, especially with people who have other high-risk behaviors, are HIV-positive, or have AIDS, People who received blood transfusions or clotting products between 1977 and 1985 (before screening for the virus became standard practice), Sexual partners of those who participate in high-risk activities (such as injection drug use or anal sex).

Symptoms of AIDS / HIV: AIDS begins with HIV infection. People infected with HIV may have no symptoms for 10 years or longer, but they can still transmit the infection to others during this symptom-free period. If the infection is not detected and treated, the immune system gradually weakens and AIDS develops. Acute HIV infection progresses over time (usually a few weeks to months) to asymptomatic HIV infection (no symptoms) and then to early symptomatic HIV infection. Later, it progresses to AIDS (advanced HIV infection with CD4 T-cell count below 200 cells/mm3 ).

Almost all people 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 damaging their immune system. 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. People with AIDS have had their immune system damaged by HIV and are very susceptible to these opportunistic infections. Common symptoms are: Chills, Fevers, Sweats (particularly at night), Swollen lymph glands, Weakness and weight loss.

Note: Initial infection with HIV may produce no symptoms. Some people, however, do experience flu-like symptoms with fever, rash, sore throat, and swollen lymph nodes, usually 2 - 4 weeks after contracting the virus. Some people with HIV infection stay symptom-free for years between the time they are exposed to the virus and when they develop AIDS.

Exams and Tests: The following is a list of AIDS-related infections and cancers that people with AIDS may get as their CD4 count decreases. In the past, having AIDS was defined as having HIV infection and getting one of these additional diseases. Today, according to the Centers for Disease Control and Prevention, a person may also be diagnosed as having AIDS if they have a CD4 cell count below 200 cells/mm3, even if they don't have an opportunistic infection. AIDS may also be diagnosed if a person develops one of the opportunistic infections and cancers that occur more commonly in people with HIV infection. These infections are unusual in people with a healthy immune system. CD4 cells are a type of immune cell. They are also called "T cells" or "helper cells." Many other illnesses and their symptoms may develop, in addition to those listed here.

Common with CD4 count below 350 cells/mm3: Herpes simplex virus -- causes ulcers/small blisters in the mouth or genitals, happens more frequently and usually much more severely in an HIV-infected person than in someone without HIV infection

Tuberculosis -- infection by tuberculosis bacteria that mostly 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 (brain and spinal cord). Oral or vaginal thrush -- yeast infection of the mouth or vagina. Herpes zoster (shingles) -- ulcers/small blisters over a patch of skin, caused by reactivation of the varicella zoster virus, the same virus that causes chickenpox, Non-Hodgkin's lymphoma -- cancer of the lymph nodes, Kaposi's sarcoma -- cancer of the skin, lungs, and bowel associated with a herpes virus (HHV-8). It can happen at any CD4 count, but is more likely to happen at lower CD4 counts, and is more common in men than in women.

Common with CD4 count below 200 cells/mm3: Pneumocystis carinii pneumonia, "PCP pneumonia," now called Pneumocystis jiroveci pneumonia, caused by a fungus, Candida esophagitis -- painful yeast infection of the esophagus, Bacillary angiomatosis -- skin lesions caused by a bacteria called Bartonella, which may be acquired from cat scratches.

Common with CD4 count below 100 cells/mm3: Cryptococcal meningitis -- fungal infection of the lining of the brain, AIDS dementia -- worsening and slowing of mental function, caused by HIV itself, Toxoplasma encephalitis -- infection of the brain by a parasite, called Toxoplasma gondii , which is frequently found in cat feces; causes lesions (sores) in the brain, Progressive multifocal leukoencephalopathy -- a disease of the brain caused by a virus (called the JC virus) that results in a severe decline in mental and physical functions, Wasting syndrome -- extreme weight loss and loss of appetite, caused by HIV itself, Cryptosporidium diarrhea -- Extreme diarrhea caused by one of the parasites that affect the gastrointestinal tract.

Common with CD4 count below 50/mm3: 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, a test called HIV RNA level (or viral load) may be used to monitor patients. Basic screening lab tests and regular cervical Pap smears are important to monitor in HIV infection, due to the increased risk of cervical cancer in women with a compromised immune system. Anal Pap smears to detect potential cancers may also be important in both HIV-infected men and women, but their value is not proven.

Treatment: There is no cure for AIDS at this time. However, a variety of treatments are available that can help keep symptoms at bay and improve the quality of life for those who have already developed symptoms. Antiretroviral therapy suppresses the replication of the HIV virus in the body. A combination of several antiretroviral drugs, called highly active antiretroviral therapy (HAART), has been very effective in reducing the number of HIV particles in the bloodstream. This is measured by the viral load (how much virus is found in the blood). Preventing the virus from replicating can improve T-cell counts and help the immune system recover from the HIV infection. HAART is not a cure for HIV, but it has been very effective for the past 12 years. People on HAART with suppressed levels of HIV can still transmit the virus to others through sex or by sharing needles.

There is good evidence that if the levels of HIV remain suppressed and the CD4 count remains high (above 200 cells/mm3), life can be significantly prolonged and improved. However, HIV may become resistant to HAART, especially in patients who do not take their medications on schedule every day. Genetic tests are now available to determine whether an HIV strain is resistant to a particular drug. This information may be useful in determining the best drug combination for each person, and adjusting the drug regimen if it starts to fail. These tests should be performed any time a treatment strategy begins to fail, and before starting therapy. When HIV becomes resistant to HAART, other drug combinations must be used to try to suppress the resistant strain of HIV. There are a variety of new drugs on the market for treating drug-resistant HIV.

Treatment with HAART has complications. HAART is a collection of different medications, each with its own side effects. Some common side effects are: Collection of fat on the back ("buffalo hump") and abdomen, General sick feeling (malaise, Nausea and Weakness. When used for a long time, these medications increase the risk of heart attack, perhaps by increasing the levels of fat and glucose (sugar) in the blood. Any doctor prescribing HAART should carefully watch the patient for possible side effects. In addition, routine blood tests measuring CD4 counts and HIV viral load should be taken every 3 months. The goal is to get the CD4 count as close to normal as possible, and to suppress the amount of HIV virus in the blood to a level where it cannot be detected.

Other antiviral medications are being investigated. In addition, growth factors that stimulate cell growth, such as erthythropoetin (Epogen) and filgrastim (G-CSF or Neupogen) 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 jiroveci pneumonia) if the CD4 count is low enough. This keeps AIDS patients healthier for longer periods of time. Opportunistic infections are treated when they happen.

When to Contact a Doctor: Call for an appointment with your health care provider if you have any of the risk factors for HIV infection, or if you develop symptoms of AIDS. By law, AIDS testing must be kept confidential. Your health care provider will review results of your testing with you.

Prevention: See the article on safe sex to learn how to reduce the chance of acquiring or spreading HIV, and other sexually transmitted diseases, Do not use illicit drugs and do not share needles or syringes. Many communities now have needle exchange programs, where you can get rid of used syringes and get new, sterile ones. These programs can also provide referrals for addiction treatment, Avoid contact with another person's blood. Protective clothing, masks, and goggles may be appropriate when caring for people who are injured, Anyone who tests positive for HIV can pass the disease to others and should not donate blood, plasma, body organs, or sperm. Infected people should tell any sexual partner about their HIV-positive status. They should not exchange body fluids during sexual activity, and should use whatever preventive measures (such as condoms) will give their partner the most protection, HIV-positive women who wish to become pregnant should seek counseling about the risk to their unborn children, and methods to help prevent their baby from becoming infected.

The use of certain medications dramatically reduces the chances that the baby will become infected during pregnancy, The Public Health Service recommends that HIV-infected women in the United States avoid breast-feeding to prevent transmitting HIV to their infants through breast milk, 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. 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 has a low risk of transmission. HIV-positive patients who are taking antiretroviral medications are less likely to transmit the virus. For example, pregnant women who are on effective treatment at the time of delivery, and who have undetectable viral loads, give HIV to their baby less than 1% of the time, compared with about 20% of the time 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. There is less information available about how effective PEP is for people exposed to HIV through sexual activity or injection drug use. However, if you believe you have been exposed, 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.