The human immunodeficiency virus (HIV) infects and destroys immune cells leaving an infected person vulnerable to diseases that do not commonly occur in people with a healthy immune system. These disorders are known as opportunistic diseases or illnesses. The occurrence of opportunistic disease distinguishes HIV infection from AIDS. The U.S. Centers for Disease Control and Prevention (CDC) has established a list of opportunistic diseases that mark the transition to AIDS. They are termed the AIDS-defining illnesses.
Pneumocystis Pneumonia
Pneumocystis pneumonia (PCP) is caused by the fungus Pneumocystis jirovecii, formerly known as Pneumocystis carinii. This organism is common in the environment. People living with HIV who are either not receiving treatment or have markedly decreased immune cells are susceptible to PCP. The CDC reports that common symptoms of PCP include progressive shortness of breath, fever, dry cough and increasing chest pain. The antibiotic medication trimethoprim-sulfamethoxazole (TMP-SMX) is prescribed to prevent and treat PCP.
Toxoplasmic Encephalitis
Toxoplasmic encephalitis (TE) is a brain infection caused by the organism Toxoplasma gondii. Common symptoms of TE include fever, headache, weakness and confusion. Seizures and coma may develop in severe cases. The CDC advises that people living with HIV should not eat undercooked or raw meat, which may be a source of Toxoplasma gondii infection. Feces from cats is another potential source of infection, especially outdoor cats. Thorough hand washing after coming in contact with the soil is also advised to prevent infection. TMP-SMX is used to prevent infection in people with markedly low immune cell counts.
Kaposi Sarcoma
The American Cancer Society explains Kaposi sarcoma is a cancer that arises from cells in the walls of blood and lymph vessels. Kaposi sarcoma (KS) grows under the skin surface causing red, purple or brown patches. A specific variant of KS, epidemic KS, occurs in people with AIDS. KS lesions can occur anywhere on the skin and in other sites including the lungs, intestines, stomach, spleen and liver. Treatments for epidemic KS may include chemotherapy, radiation therapy and surgery.
Cryptosporidiosis
Cryptosporidiosis is a parasitic infection caused by various species of Cryptosporidium. Cryptosporidium inhabits the intestines of infected humans and animals; the organism passes with the feces. The CDC notes that Cryptosporidium is highly resistant to killing. Public water systems that use chlorine-based disinfectants are vulnerable to contamination because the organisms may not be killed by this purification technique. Cryptosporidiosis causes an acute intestinal illness characterized by watery diarrhea, nausea, vomiting, abdominal cramps and fever. In people with a normal immune system, the illness typically clears within two weeks. People with HIV and markedly decreased immune cells, however, have a more severe and protracted illness. The pancreas, lungs and bile system may be involved in the infection. Because Cryptosporidium is common in the environment, it can be contracted from many sources including unsterilized water, contaminated foods and contact with the stool of infected persons. Scrupulous hand washing to avoid inadvertent ingestion from contamination of the hands is an important means of prevention.
References
- U.S. Centers for Disease Control and Prevention, MMWR: Guidelines for Prevention and Treatment of Opportunistic Infections in HIV-Infected Adults and Adolescents
- U.S. Centers for Disease Control and Prevention, MMWR: AIDS-Defining Conditions
- University of California, San Francisco, HIVInSite: Opportunistic Infections and AIDS-Related Cancers
- Merck Manual for Healthcare Professionals: HIV, Prevention of Opportunistic Infections
- U.S. Centers for Disease Control and Prevention: Pneumocystis
