HIV infection weakens your immune system, making you highly susceptible to a large number of bacterial, viral, fungal and parasitic infections. You may also be vulnerable to certain types of cancers. But treatment with anti-retroviral drugs has markedly decreased the number of opportunistic infections and cancers affecting people with HIV. It's now more likely these infections will occur in people who have not had treatment.
• Bacterial pneumonia. Dozens of types of bacteria can cause bacterial pneumonia, which may develop on its own or after you've had an upper respiratory infection such as a cold or the flu.
• Mycobacterium avium complex (MAC). This infection is caused by a group of mycobacteria referred to by a single name — MAC. The mycobacteria normally cause an infection of the respiratory tract. But if you have advanced HIV infection and your CD4 lymphocyte count is less than 50, you're more likely to develop a systemic infection that can affect almost any internal organ, including your bone marrow, liver or spleen. MAC causes nonspecific symptoms such as fever, night sweats, weight loss, stomach pain and diarrhea.
• Tuberculosis (TB). In resource-poor nations, TB is the most common opportunistic infection associated with HIV and a leading cause of death among people living with AIDS. Millions of people are currently infected with both HIV and tuberculosis, and many experts consider the two diseases twin epidemics. That's because HIV/AIDS and TB have a deadly symbiotic relationship, in which each fuels the progress of the other. Having HIV makes you more susceptible to TB and far more likely to progress from dormant to active HIV infection. At the same time, TB increases the rate at which the AIDS virus replicates. What's more, TB often strikes people with HIV years before other problems associated with HIV develop. One of the first indications of HIV infection may be the sudden onset of TB — often in a site outside the lungs. If you're HIV-positive, you should have a simple skin test for TB early in your medical care. If the test is positive, you'll also need a chest X-ray and other appropriate tests to make sure you don't have an active infection. If your TB isn't active, there are treatments to prevent it from becoming active. TB is more worrisome than many other opportunistic infections because it's highly contagious. Multidrug-resistant tuberculosis, in which the disease resists treatment with traditional antibiotics, is of particular concern to people with HIV/AIDS.
• Salmonellosis. You contract this bacterial infection from contaminated food or water. Symptoms include severe diarrhea, fever, chills, abdominal pain and, occasionally, vomiting. Although anyone exposed to salmonella bacteria can become sick, salmonellosis is far more common in people who are HIV-positive. You can reduce your risk by washing your hands carefully after handling food and animals and by cooking meat and eggs thoroughly.
• Bacillary angiomatosis. This infection, caused by Bartonella henselae bacteria, first appears as purplish to bright red patches on your skin. It often resembles Kaposi's sarcoma, but it can cause disease in other parts of your body, including your liver and spleen.
• Cytomegalovirus (CMV). This common herpesvirus is transmitted in body fluids such as saliva, blood, urine, semen and breast milk. But a healthy immune system inactivates the virus, and it remains dormant in your body. If your immune system weakens, the virus resurfaces, causing damage to your eyes, digestive tract, lungs or other organs. Most commonly, CMV causes infection and inflammation of your retina (CMV retinitis). If not treated, CMV retinitis can lead to blindness.
• Viral hepatitis. Viral hepatitis is a viral infection of the liver. Signs and symptoms include yellowing of your skin and the whites of your eyes (jaundice), fatigue, nausea, abdominal pain, loss of appetite and diarrhea. There are several types of viral hepatitis, but the most common are hepatitis A, B and C. Hepatitis B and C can lead to persistent or chronic infection and put you at risk of long-term complications such as cirrhosis or liver cancer. If you are HIV-positive and also have hepatitis, you may be more likely to develop liver toxicity from your medications.
• Herpes simplex virus (HSV). HSV, which usually causes genital herpes, may be transmitted during unprotected anal or vaginal sex. Initial symptoms include pain or irritated skin in the genital area. Later, sores that ooze and bleed erupt on the genitals, buttocks and anus. Although these sores eventually heal, the virus periodically reappears, causing the same symptoms. If you have HIV, your skin infection is likely to be more severe than it would be in people who don't have HIV, and the sores may take longer to heal. Systemic symptoms may also be more severe. Although the herpes virus isn't life-threatening in adults, it may cause brain damage and blindness.
• Human papillomavirus (HPV). This is one of the most common causes of sexually transmitted disease. Some types of this virus cause common warts. Other types cause warts on the genitals. If you're HIV-positive, you're especially susceptible to infection with HPV and more prone to recurrent infections. HPV infection is especially serious because it significantly increases a woman's risk of cervical cancer. Infection with both HPV and HIV increases a woman's risk even further — cervical cancer seems to occur more often and more aggressively in women who are HIV-positive. In 2006, the Food and Drug Administration approved the first vaccine to offer protection from the most dangerous types of HPV. The vaccine is most effective when given to girls before they become sexually active, but it also provides protection for sexually active women age 26 and younger. If you are not a candidate for the vaccine, are HIV-positive or have unprotected sex with more than one partner, you should have a Pap test — a test that examines cells taken from the cervix — every year to check for cervical cancer, HPV and other sexually transmitted diseases. Anyone who engages in anal sex should be tested for anal cancer because HPV increases the risk of this type of cancer in both men and women.
• Progressive multifocal leukoencephalopathy (PML). PML is an extremely serious brain infection caused by the human polyomavirus JC virus. Signs and 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 usually occurs only when your immune system has been severely damaged.
• Candidiasis. Candidiasis is a common HIV-related infection. It causes inflammation and a thick white coating on the mucous membranes of your mouth, tongue (thrush), esophagus (Candida esophagitis) or vagina. Children may have especially severe symptoms in the mouth or esophagus, which can make eating painful and difficult.
• Cryptococcal meningitis. Meningitis is an inflammation of the membranes and fluid surrounding your brain and spinal cord (meninges). Cryptococcal meningitis is a common central nervous system infection associated with HIV, caused by a fungus that is present in soil. It may also be associated with bird or bat droppings. Symptoms include headache, high fever, a stiff neck and sensitivity to light. Cryptococcal meningitis can be successfully treated with antifungal medications, but early treatment is essential. Meningitis is a serious disease that can cause severe complications or prove fatal in a short period of time. Once you've had cryptococcal meningitis, you'll need to be on long-term medication to prevent a recurrence.
• Pneumocystis carinii pneumonia (PCP). Although anti-retroviral drugs have helped reduce the number of cases of PCP, it remains one of the most common opportunistic infections affecting people with AIDS in the United States. PCP attacks the lungs, making it difficult to breathe. Signs and symptoms include a cough that doesn't go away, fever and trouble breathing.
• Toxoplasmosis. This potentially deadly infection is caused by Toxoplasma gondii, a parasite spread primarily by cats. Infected cats pass the parasites in their stool, and the parasites may then spread to other animals. Humans generally contract toxoplasmosis by touching their mouths with their hands after changing cat litter or by eating raw or undercooked meat, especially pork, lamb and venison. Once you're infected, the parasites can spread to every organ in your body, including your heart, eyes and lungs. For many people with AIDS, toxoplasmosis leads to encephalitis, an infection of the brain. Signs and symptoms may include disorientation, seizures, and difficulty walking or speaking.
• Cryptosporidiosis. This infection is caused by an intestinal parasite that's commonly found in animals. You contract cryptosporidiosis when you ingest contaminated food or water. The parasite grows in your intestines and bile ducts, leading to severe, chronic diarrhea in people with AIDS.
• Kaposi's sarcoma. Kaposi's sarcoma is a tumor of the blood vessel walls. Although rare in people not infected with HIV, it's common in HIV-positive people. Kaposi's sarcoma usually appears as pink, red or purple lesions on the skin and mouth. In people with darker skin, the lesions may look dark brown or black. Kaposi's sarcoma can also affect the internal organs, including the digestive tract and lungs. Researchers are testing new combinations of the chemotherapy drugs currently used to treat Kaposi's sarcoma as well as new ways of delivering those medications. What's more, as with most opportunistic infections associated with AIDS, the use of anti-retrovirals has reduced the incidence of this cancer and has even reduced the lesions in people already affected.
• Non-Hodgkin's lymphoma. This cancer originates in lymphocytes, a type of white blood cell. Lymphocytes are concentrated in your bone marrow, lymph nodes, spleen, digestive tract and skin. Although lymphomas can start in other organs, they usually begin in your lymph nodes. The most common early sign is painless swelling of the lymph nodes in your neck, armpit or groin.
• Wasting syndrome. Aggressive treatment regimens have reduced the number of cases of wasting syndrome, but it does still affect many people with AIDS. It is defined as a loss of at least 10 percent of body weight and is often accompanied by diarrhea, chronic weakness and fever.
• Neurological complications. Although AIDS doesn't appear to infect the nerve cells, it can still cause neurological symptoms such as confusion, forgetfulness, changes in behavior, depression, anxiety and trouble walking. One of the most common neurological complications is AIDS dementia complex, which leads to behavioral changes and diminished mental functioning.