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 depleted by HIV and are very susceptible to these opportunistic infections. Common symptoms are fevers, sweats (particularly at night), swollen lymph 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 may produce no symptoms. Some people, however, do experience flu-like symptoms with fever, rash, sore throat, and swollen lymph nodes, usually 2 weeks after contracting the virus. Some people with HIV infection remain without symptoms for years between the time they are exposed to the virus and when they develop AIDS.

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, 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 corresponding symptoms may develop in addition to those listed here.

Common with CD4 count below 350 cells/mcl:

• 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 the 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
• 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). 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/mcl:

• Pneumocystis carinii pneumonia, "PCP pneumonia," now called Pneumocystis jiroveci pneumonia
• 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/mcl:

• 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 gondi, which is frequently found in cat feces; causes lesions (sores) 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 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/mcl:

• 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 immunocompromised women. Anal Pap smears to detect potential cancers may also be important in both HIV infected men and women.