Acquired immunedeficiency syndrome (AIDS) is a disease caused by the human immunedeficiency virus (HIV). According to the National Institute of Allergy and Infectious Diseases (NIAID), there are over 30 million people worldwide living with HIV/AIDS, and about one million of them live in the U.S.
The destruction of the immune system caused by HIV/AIDS opens the way for opportunistic infections by bacteria, viruses and fungi. According to AIDS.gov, these diseases are considered opportunistic because they take advantage of a devastated immune system and cause severe disease. The Centers for Disease Control and Prevention (CDC) classifies these diseases as AIDS defining illnesses.
Bacterial Infections
Tuberculosis, an infection caused by Mycobacterium tuberculosis, is one notable bacterial illness that is common in AIDS patients. According to the Mayo Clinic, it is a leading cause of death among HIV/AIDS patients and the most common opportunistic infection in poorer countries. The infection usually affects the lungs, but can also affect the bones, kidneys, brain and digestive system. Mycobacterium avium complex (MAC) is an illness caused by an organism closely related to mycobacterium tuberculosis that also affects different organs of the body.
Other bacterial infections include recurrent bacterial pneumonia, skin sepsis, bacillary angiomatosis or bartonellosis, recurrent salmonella infections and other bacterial infections of the digestive system.
Viral Infections
Cytomegalovirus (CMV) causes widespread infection in HIV/AIDS patients, affecting the lungs, eyes and digestive tract. If untreated, according to the Mayo Clinic, CMV infection in the eye could lead to blindness.
Herpes simplex virus (HSV), which usually causes genital herpes, attacks the brain and eyes. It can cause brain damage and blindness in HIV/AIDS patients.
Viral related cancers like Kaposi's sarcoma--caused by human herpes virus 8 (HHV8)--and invasive cervical cancer--caused by human papilloma virus (HPV)--are also seen in HIV/AIDS patients. These patients are also suceptible to Varicella zoster, or shingles, hepatitis from hepatitis A, B and C viruses, progressive multifocal leukoencephalopathy (PML) from human polyoma virus and dementia caused by HIV.
Fungal Infections
Thrush, caused by candida albicans, affects the mouth and throat in HIV/AIDS patients. Thrush is especially severe in children, according to the Mayo Clinic, making swallowing food and drinks a very painful experience.
Cryptococcal meningitis is another fungal infection seen in HIV/AIDS patients. This illness affects the coverings of the brain and spinal cord. Other fungal infections seen in HIV/AIDS are histoplasmosis, coccidiomycosis and aspergillosis.
Cancers
In addition to cancers linked to viral infections, lymphoma, which involves the lymphoid tissues, develops in HIV/AIDS patients. Non-Hodgkin's lymphoma is the predominant type of this disease, but Hodgkin's lymphoma is also common in HIV/AIDS patients.
Parasitic Infections
Pneumocystis carinii pneumonia (PCP), caused by the parasite Pneumocystis jirovecii, is one of the most common opportunistic infections in HIV/AIDS patients in the U.S., according to the Mayo Clinic.
Another parasitic infection of importance in HIV/AIDS patients is toxoplasmosis, which is caused by the parasite Toxoplasma gondii and is commonly spread by cats. This disease attacks the brain and is potentially fatal.
Isosporiasis and cryptosporidiosis are two causes of very troublesome diarrhea in HIV/AIDS patients, and they contribute immensely to the weight loss seen in the later stages of the illness.
In resource-poor nations, malaria and Chaga's disease also infect HIV/AIDS patients.
