More than 790,000 cases of AIDS have been reported in the United States since 1981, and as many as 900,000 Americans may be infected with HIV. The epidemic is growing most rapidly among minority populations and is a leading killer of African-American males ages 25 to 44. According to the United States Centers for Disease Control and Prevention (CDC), AIDS affects nearly seven times more African Americans and three times more Hispanics than whites.

Learn more about:

• Transmission of HIV
• HIV—Early Symptoms
• AIDS
• Diagnosis of HIV
• Treatment
• Prevention
• Current Research

HIV—Early Symptoms
The symptoms of HIV and AIDS vary, depending on the phase of infection. When first infected with HIV, you may have no symptoms at all, although it's more common to develop a brief flu-like illness 2 to 6 weeks after becoming infected. But because the symptoms of an initial infection—which may include fever, headache, sore throat, swollen lymph glands and rash—are similar to those of other diseases, you might not realize you've been infected with HIV.

Even if you don't have symptoms, you're still able to transmit the virus to others. Once the virus enters your body, your own immune system also comes under attack. The virus multiplies in your lymph nodes and slowly begins to destroy your helper T cells (CD4 lymphocytes), the white blood cells that coordinate your entire immune system.

You may remain symptom-free for 8 or 9 years. But the virus continues to multiply and destroy immune cells. Tests are likely to show a sharp decline in the number of these cells in your blood. Eventually, you may develop mild infections or chronic symptoms such as:

• Swollen lymph nodes, often one of the first signs of HIV infection
• Diarrhea
• Weight loss
• Fever
• Cough and shortness of breath

AIDS
The term AIDS applies to the most advanced stages of HIV infection. The Center for Disease Control and Prevention (CDC) developed official criteria for the definition of AIDS and is responsible for tracking the spread of AIDS in the United States.

CDC's definition of AIDS includes all HIV-infected people who have fewer than 200 CD4 positive T cells per cubic millimeter of blood. (Healthy adults usually have CD4 positive T-cell counts of 1,000 or more.) In addition, the definition includes 26 clinical conditions that affect people with advanced HIV disease. Most of these conditions are opportunistic infections that generally do not affect healthy people. In people with AIDS, these infections are often severe and sometimes fatal because the immune system is so ravaged by HIV that the body cannot fight off certain bacteria, viruses, fungi, parasites, and other microbes.

Symptoms of opportunistic infections common in people with AIDS include:

• Coughing and shortness of breath
• Seizures and lack of coordination
• Difficult or painful swallowing
• Mental symptoms such as confusion and forgetfulness
• Severe and persistent diarrhea
• Fever
• Vision loss
• Nausea, abdominal cramps, and vomiting
• Weight loss and extreme fatigue
• Severe headaches
• Coma

Children with AIDS may get the same opportunistic infections as do adults with the disease. In addition, they also have severe forms of the bacterial infections all children may get, such as conjunctivitis (pink eye), ear infections, and tonsillitis.

People with AIDS are particularly prone to developing various cancers, especially those caused by viruses such as Kaposi's sarcoma and cervical cancer, or cancers of the immune system known as lymphomas. These cancers are usually more aggressive and difficult to treat in people with AIDS. Signs of Kaposi's sarcoma in light-skinned people are round brown, reddish, or purple spots that develop in the skin or in the mouth. In dark-skinned people, the spots are more pigmented.

During the course of HIV infection, most people experience a gradual decline in the number of CD4 positive T cells, although some may have abrupt and dramatic drops in their CD4 positive T-cell counts. A person with CD4 positive T cells above 200 may experience some of the early symptoms of HIV disease. Others may have no symptoms even though their CD4 positive T-cell count is below 200.

Many people are so debilitated by the symptoms of AIDS that they cannot hold steady employment or do household chores. Other people with AIDS may experience phases of intense life-threatening illness followed by phases in which they function normally.

A small number of people first infected with HIV 10 or more years ago have not developed symptoms of AIDS. Scientists are trying to determine what factors may account for their lack of progression to AIDS, such as particular characteristics of their immune systems or whether they were infected with a less aggressive strain of the virus, or if their genes may protect them from the effects of HIV. Scientists hope that understanding the body's natural method of control may lead to ideas for protective HIV vaccines and use of vaccines to prevent the disease from progressing.

Treatment
When AIDS first surfaced in the United States, there were no medicines to combat the underlying immune deficiency and few treatments existed for the opportunistic diseases that resulted. During the past 10 years, however, researchers have developed drugs to fight both HIV infection and its associated infections and cancers.

The U.S. Food and Drug Administration (FDA) has approved a number of drugs for treating HIV infection. The first group of drugs used to treat HIV infection, called nucleoside reverse transcriptase (RT) inhibitors, interrupts an early stage of the virus making copies of itself. Included in this class of drugs (called nucleoside analogs) are AZT, ddC (zalcitabine), ddI (dideoxyinosine), d4T (stavudine), 3TC (lamivudine), abacavir (ziagen), and tenofovir (viread). These drugs may slow the spread of HIV in the body and delay the start of opportunistic infections.

Health care providers can prescribe non-nucleoside reverse transcriptase inhibitors (NNRTIs), such as delvaridine (Rescriptor), nevirapine (Viramune), and efravirenz (Sustiva), in combination with other antiretroviral drugs.

More recently, FDA has approved a second class of drugs for treating HIV infection. These drugs, called protease inhibitors, interrupt virus replication at a later step in its life cycle. They include:

• Ritonavir (Norvir)
• Saquinivir (Invirase)
• Indinavir (Crixivan)
• Amprenivir (Agenerase)
• Nelfinavir (Viracept)
• Lopinavir (Kaletra)

Because HIV can become resistant to any of these drugs, health care providers must use a combination treatment to effectively suppress the virus. When RT inhibitors and protease inhibitors are used in combination, it is referred to as highly active antiretroviral therapy, or HAART, and can be used by people who are newly infected with HIV as well as people with AIDS.

Researchers have credited HAART as being a major factor in significantly reducing the number of deaths from AIDS in this country. While HAART is not a cure for AIDS, it has greatly improved the health of many people with AIDS and it reduces the amount of virus circulating in the blood to nearly undetectable levels. Researchers, however, have shown that HIV remains present in hiding places, such as the lymph nodes, brain, testes, and retina of the eye, even in patients who have been treated.

Despite the beneficial effects of HAART, there are side effects associated with the use of antiviral drugs that can be severe. Some of the nucleoside RT inhibitors may cause a decrease of red or white blood cells, especially when taken in the later stages of the disease. Some may also cause inflammation of the pancreas and painful nerve damage. There have been reports of complications and other severe reactions, including death, to some of the antiretroviral nucleoside analogs when used alone or in combination. Therefore, healthcare experts recommend that people on antiretroviral therapy be routinely seen and followed by their health care providers. The most common side effects associated with protease inhibitors include nausea, diarrhea, and other gastrointestinal symptoms. In addition, protease inhibitors can interact with other drugs resulting in serious side effects.

A number of drugs are available to help treat opportunistic infections to which people with HIV are especially prone. These drugs include:

• Foscarnet and ganciclovir to treat cytomegalovirus (CMV) eye infections
• Fluconazole to treat yeast and other fungal infections
• Trimethoprim/sulfamethoxazole (TMP/SMX) or pentamidine to treat Pneumocystis carinii pneumonia (PCP)

In addition to antiretroviral therapy, health care providers treat adults with HIV, whose CD4+ T-cell counts drop below 200, to prevent the occurrence of PCP, which is one of the most common and deadly opportunistic infections associated with HIV. They give children PCP preventive therapy when their CD4+ T-cell counts drop to levels considered below normal for their age group. Regardless of their CD4+ T-cell counts, HIV-infected children and adults who have survived an episode of PCP take drugs for the rest of their lives to prevent a recurrence of the pneumonia.

HIV-infected individuals who develop Kaposi's sarcoma or other cancers are treated with radiation, chemotherapy, or injections of alpha interferon, a genetically engineered naturally occurring protein.