Causes

Important facts about the spread of AIDS include:

• AIDS is the sixth leading cause of death among people ages 25 - 44 in the United States, down from number one in 1995.
• The World Health Organization estimates that more than 25 million people worldwide have died from this infection since the start of the epidemic
• In 2008, there were approximately 33.4 million people around the world living with HIV/AIDS, including 2.1 million children under age 15.

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
• 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

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 nonprogressors, 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
• 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)
• Headache
• Nausea
• 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