As more serious symptoms and complications appear, the HIV infection may then meet the official definition of AIDS: a positive HIV-antibody test, and either the onset of an "AIDS defining" infection or cancer (see below), or a CD4 lymphocyte count of 200/ml or less (a normal count ranges from 600/ml to 1000/ml).

HIV

Initial infection with the HIV virus may produce no symptoms. The length of time between initial HIV infection and the development of AIDS varies greatly, and some people may remain without symptoms for years. Even if a person does not have symptoms, the virus can still be transmitted to others.

It is common to develop a brief flu-like illness 2 to 6 weeks after being infected. The symptoms may include fever, headache, sore throat, swollen lymph glands, and rash. These symptoms are similar to many other diseases and may go unrecognized as HIV infection.

Many people remain symptom free for 8 or 9 years, but, during this time the virus continues to multiply and destroy immune cells. The Centers for Disease Control (CDC) suggests the following may be warning signs of HIV infection, but cautions that any of these symptoms can be related to other illness, and that only an HIV blood test can be used for an accurate diagnosis:

During the last phase of HIV, which can occur up to 10 or 11 years after the initial infection, the immune system has been severely damaged, making the body highly susceptible to a large number of bacterial, viral, fungal and parasitic (opportunistic) infections. The symptoms of some of these infections may include:

People with HIV infection are also at greater risk of developing certain cancers, especially Kaposi's sarcoma, cervical cancer and lymphoma.

Children who are HIV positive often fail to gain weight or grow normally. As the disease progresses, they may have difficulty walking or delayed mental development. They may also develop cerebral palsy. In addition, children are susceptible to the same opportunistic infections as adults and may have severe forms of common childhood illnesses such as ear infections (otitis media), pneumonia, and tonsillitis.

AIDS

The symptoms of AIDS are primarily the result of infections (called opportunistic infections) that do not normally develop in individuals with healthy immune systems. In order for a patient who is infected with HIV to have AIDS, the immune system must be severely damaged. The severity of the immune system damage is measured by a CD4 lymphocyte count. If a person infected with HIV has a CD4 count less than 200/ml, they are said to have AIDS.

The Centers for Disease Control (CDC) considers the following list of conditions as "AIDS-defining". Many other illnesses and corresponding symptoms may develop in addition to those listed here:

Tuberculosis is the most common opportunistic infection associated with HIV worldwide. Tuberculosis is an infection by the tuberculosis bacterium that predominantly affects the lungs, but can spread through the blood and lymph nodes to the rest of the body in people with HIV.

TB causes a long-term cough that may produce blood, and may also cause fever, weight loss and night sweats. The disease can strike people with HIV no matter what their level of CD4 lymphocytes, which means TB can often occur years before other problems associated with HIV develop.

Everyone who is HIV-positive should have a simple skin test for TB. If the test is positive, a chest X-ray and other tests will determine if the infection is active. If the TB is not active, preventative treatments are available.

Tuberculosis is more worrisome than many other opportunistic infections because of the ease with which it is spread (by coughing or sneezing) from one person to another. Multidrug Resistant Tuberculosis (MDR-TB), is resistant to traditional treatments and is of particular concern to people with HIV and AIDS.

Anyone with HIV can get Tuberculosis, but it is more likely in those with CD4 counts of less than 200/ml.

Herpes Simplex Virus, which usually causes genital herpes, may be transmitted during unprotected sex. Initial symptoms include pain or irritated skin in the genital area, and later sores that erupt and ooze and bleed. Although these sores eventually heal, the virus periodically reappears, causing the same symptoms. The symptoms of HSV are more severe in people with HIV and the sores may take longer to heal. The herpes virus isn't life-threatening in adults, but it may cause brain damage, blindness or death in infants infected during delivery.

Anyone with HIV can get Herpes Simplex, regardless of CD4 count.

Candidiasis (Thrush) is a yeast infection of the mouth or genitals, and is a very common HIV-related infection. The symptoms include inflammation and a thick white coating on the mucous membranes of the mouth, tongue, vagina or esophagus (Candida esophagitis). Children may have especially severe symptoms in the mouth or esophagus, which can make eating painful and difficult. Candidiasis of the bronchi, trachea, lungs or esophagus is considered "AIDS-defining".

Anyone with HIV can get Candidiasis, but it is more dangerous in those with CD4 counts of less than 200/ml.

Non-Hodgkin's Lymphoma is a cancer of the lymph glands originating in the lymphocytes, a type of white blood cell involved in fighting infection. NHL usually starts in the lymph nodes, but can also start in the liver, lungs or gastrointestinal tract. The most common symptom of NHL is swollen (usually painless) lymph nodes in the neck, armpit or groin. Other symptoms include fever, night sweats, fatigue, itchy skin and weight loss, aches, and sometimes coughing, difficulty breathing and chest pain.

Anyone with HIV can get Non-Hodgkin's Lymphoma, but it is more likely in those with CD4 counts of less than 200/ml.

Salmonellosis (food poisoning) is an infection caused by the salmonella bacterium, which is contracted from contaminated food or water. Symptoms include severe diarrhea, fever, chills, abdominal pain and sometimes vomiting. The risk of contracting salmonellosis can be reduced by hand washing, and by cooking meat and eggs thoroughly.

Anyone with HIV can get Salmonellosis, regardless of CD4 count.

Bacillary Angiomatosis ("Cat Scratch Disease") is an infection that first appears as purplish to bright red patches on the skin (often resembling Kaposi's sarcoma). As the infection progresses, symptoms include fever, sweats, chills, poor appetite, vomiting and weight loss.

Anyone with HIV can get Bacillary Angiomatosis, but it is more likely in those with CD4 counts of less than 500/ml.

Viral hepatitis is a viral infection of the liver. Symptoms include yellowing of the skin and the whites of the eyes (jaundice), fatigue, nausea, abdominal pain, loss of appetite and diarrhea. There are several types of hepatitis, but the most common types are Hepatitis A, B and C.

Hepatitis A is contracted from contaminated food and water, and through poor hygiene. Hepatitis B is contracted through body fluid. Those at risk for Hepatitis B are also at risk for Hepatitis C . Hepatitis B and C can lead to chronic infection and increase the risks for long-term complications such as cirrhosis or liver cancer.

Anyone with HIV can get Viral Hepatits, regardless of CD4 count.

Human Papillomavirus is one of the most common causes of sexually transmitted disease . Some types of this virus cause common warts, while others cause warts on the genitals. HPV infection is especially serious because it puts women at risk for cervical cancer; the risk is increased further in women with HIV.

Anyone with HIV can get Human Papillomavirus, but women with CD4 counts of less than 500/ml are more likely to develop HPV-related growths in the cervix.

Cryptosporidiosis is an infection contracted by ingesting contaminated food or water. The parasite grows in the intestines and bile ducts and can cause severe chronic diarrhea.

Anyone with HIV can get Cryptosporidiosis, however it is particularly dangerous for those with a CD4 count of 50/ml or less.

Pneumocystitis Carinii Pneumonia (PCP) is the most common opportunistic infection that occurs with AIDS in the United States. The germ that causes the PCP infection is spread though breathing or coughing. Symptoms include persistent cough, fever, trouble breathing (lips and nail-beds may become blue), fatigue, and weight loss.

PCP is particularly dangerous for those with a CD4 count of less than 200/ml.

Kaposi's Sarcoma is the most common AIDS-related cancer. It is a tumor of the blood vessel walls. Common symptoms are pink, red or purple lesions on the skin and in the mouth. The first spots, sores or bumps usually appear on the face, nose, mouth, arms, upper body or legs. The lesions vary from pinhead size to the size of a large coin, and may be painless. Sometimes the skin lesions are painful and can cause itching; and sores in the mouth or throat may cause eating or swallowing problems. Kaposi's Sarcoma can also affect the internal organs, including the digestive tract, lymph nodes and lungs.

Anyone with HIV can get Kaposi's Sarcoma, but it is more likely in those with CD4 counts of less than 200/ml.

Cryptococcal meningitis, caused by a fungus, is the most common central nervous system infection associated with HIV. Meningitis is an inflammation of the membranes and fluid surrounding the brain and spinal cord (meninges). Symptoms include headache, high fever, stiff neck, and sensitivity to light. Meningitis is a serious disease that can cause severe complications or prove fatal in a short amount of time.

Cryptococcal Meningitis is particularly dangerous in those with a CD4 count of 50/ml or less.

Toxoplasmosis, caused by a parasite spread primarily by cats, is the most common cause of brain lesions in people with advanced HIV disease where toxoplasmosis often leads to encephalitis, an infection of the brain. Symptoms may include disorientation, seizures, fatigue, headaches and difficulty walking or speaking.

Toxoplasmosis is particularly dangerous in those with a CD4 count of 50/ml or less.

Progressive Multifocal Leukoencephalopathy is an extremely serious viral disease of the brain. PML causes a quick decline in cognitive and motor functions. Symptoms vary, and may include speech problems, weakness on one side of the body, loss of vision in one eye, or numbness in one arm or leg.

PML is a late-stage disease that occurs only when the immune system is severely damaged.

Mycobacterium Avium Complex is a common AIDS infection caused by a bacterium related to tuberculosis. Normally, the bacterium causes an infection of the respiratory tract, but, in advanced HIV or AIDS, a systemic infection can affect almost any internal organ, including the bone marrow, liver or spleen. MAC causes nonspecific symptoms such as cough, fever, night sweats, weight loss, fatigue, stomach pain, and diarrhea.

MAC is particularly dangerous in those with a CD4 count of 50/ml or less.

Cytomegalovirus infection is a viral infection that can affect almost any organ system. A healthy immune system inactivates the virus, and it therefore remains dormant in the body. If the immune system weakens, the virus resurfaces. Symptoms include fatigue, fever, enlarged lymph nodes, and pain in the muscles or throat. CMV can cause damage to the eyes (retinitis), digestive tract (diarrhea), lungs (pneumonia), liver (hepatitis), or other organs.

CMV is particularly dangerous in those with a CD4 count of 100/ml or less.

Wasting Syndrome: extreme weight loss and anorexia caused by HIV.
AIDS Dementia: worsening and slowing of mental function caused by HIV.