Acquired Immune Deficiency Syndrome (AIDS)
Acquired Immune Deficiency Syndrome (AIDS)
(See also Kaposi's Sarcoma and Pneumocystis carinii Pneumonia). A terminal, secondary immunodeficiency syndrome characterized by dysfunction of cell-mediated immunity and manifested by opportunistic infections and malignancies.
Causes and Incidence
The cause is thought to be one of several related retroviruses (human immunodeficiency virus, or HIV) that convert viral RNA into a proviral DNA copy, which is incorporated into the DNA of the host cell. The proviral copy then is duplicated with normal cellular genes during each cellular division. HIV is a blood-borne virus and commonly is transmitted through exchange of body fluids during sexual contact, through parenteral exposure or fetal exposure to blood, and through select body fluids from an individual infected with HIV. Infants are at risk of acquiring the HIV during fetal development, delivery, or breast-feeding from an HIV-positive mother. High-risk behavior for HIV exposure includes unprotected sexual activity and IV drug use with shared needles.
Occupational transmission to health care workers is possible through needle sticks or other exposure to HIV-infected blood. Individuals infected with HIV who are asymptomatic are in a carrier state and may transmit the disease without displaying any of the characteristic signs of AIDS.
AIDS is a global pandemic, and it is predicted that more than 110 million people worldwide will be infected with HIV by the end of the century. As of 1991 more than 1.1 million people worldwide had died.
In the United States the incidence of AIDS has steadily increased from 3.46 per 100,000 population in 1985 to 40.20 per 100,000 population in 1993. Although it is far too early to interpret the reasons, in 1994 the incidence of reported AIDS cases dropped slightly, to 30.07 per 100,000 population. All races and ethnic groups are affected. Currently men far outnumber women as victims of the disease. However, the fastest rise in cases is occurring among minority women. The median age range for all individuals with AIDS is 30 to 39 years.
The current theory holds that as HIV is reproduced, it affects the immune system by infecting the T-helper cell lymphocytes, which usually coexist in a 2:1 ratio with T-suppressor cells. As the viruses replicate, masquerading as helper cells, the number of real helper cells declines, and the T-suppressor cells eventually dominate, leading to immunosuppression and a lowering of the body's prime defense mechanism against intracellular pathogens and the formation of malignant tumors.
AIDS is a chronic, progressive, terminal illness that can be divided into four stages, as defined by the federal Centers for Disease Control and Prevention (CDC):
An acute, flulike syndrome that develops at the time of initial infection and lasts from days to weeks
An asymptomatic, HIV-positive carrier state that may persist for years
Generalized, persistent lymphadenopathy
The development of other disease processes, including (1) constitutional disease (weight loss greater than 10% of body weight, persistent diarrhea, fever, malaise, oral thrush); (2) neurologic disease (peripheral neuropathies, paresthesia, myelopathy, dementia); (3) opportunistic infections (bacterial, viral, fungal, or protozoal) and their accompanying clinical features; (4) secondary neoplasms; and (5) other conditions (e.g., endocarditis, interstitial pneumonitis, immune thrombocytopenic purpura)
The complications are numerous and are associated with the various opportunistic infections or neoplasms, as well as the repetitive nature of the infections. These infections eventually overwhelm the body's compromised immune system, leading to massive infectious invasions in every body system and, eventually, death.
Any of the above manifestations; history of high-risk behavior
Enzyme-linked immunosorbent assay (ELISA)
Screening test for HIV antibody (may be positive from 0 to 12 months after exposure)
Western blot/ immunofluorescent assay
To confirm reactive seropositive results obtained by ELISA test
Reduced reactivity and function of T cells; reduced number of T-helper cells, increased number of T-suppressor cells
Numbers and function normal or increased
Natural killer (NK) cells
Normal or increased
Tumor excision of some related neoplasms
Experimental treatment with various retroviral drugs such as zidovudine (Retrovir; formerly azidothymidine [AZT]); didanosine (Videx; formerly dideoxyinosine [ddI]; and zalcitabine (Hivid; formerly dideoxycytidine [ddC]), using CD4 lymphocyte counts as a treatment guide; prophylaxis with trimethoprim-sulfamethoxazole tablets to prevent Pneumocystis carinii pneumonia (PCP); rifabutin prophylaxis for Mycobacterium avium infection; drugs specific for various opportunistic infections; chemotherapy for carcinomas; prophylactic use of zidovudine following exposure through penetrating injuries is controversial
Measures to improve overall health (e.g., no smoking, balanced nutrition, drug rehabilitation, flu vaccine, pneumococcal vaccine, hepatitis B vaccine); supportive measures for coping with and adapting to the effects of the disease (e.g., counseling, support groups); instruction in how the disease is spread in order to promote prevention, particularly among high-risk groups; use of universal precautions by health care workers and family members to prevent transmission.