The first cases of an illness later named Acquired Immunodeficiency Syndrome (AIDS) were detected in early 1981, and the first description, based on five cases, was reported in the June 6, 1981 issue of Morbidity and Mortality Weekly Report (MMWR), a publication of the U.S. Centers for Disease Control (CDC). The original cases were in homosexual men, but in 1982, cases also appeared in people with hemophilia and in others receiving transfusions of blood and blood products. Cases also began to be reported in intravenous (IV) drug abusers who shared needles. Hence, by 1983, the possible causes had been narrowed to an infectious agent that could be transmitted by sexual intercourse (anal or vaginal) and by infected blood and blood products.
As of August 31, 1987, 40,795 cases in adults and 571 in children had been reported to CDC. In adults, 26,968 cases or 66 percent were in homosexual or bisexual men, and 9,786 or 24 percent in IV drug abusers. All other categories - transfusions, heterosexual transmission, and undetermined - accounted for 5 percent or less each. In children, 78 percent of cases involve an infected mother, since AIDS is transmitted by the mother's blood before or during birth, with an additional 17 percent due to transfusions of blood or blood products. The reported cases by year demonstrate the growth of this epidemic.
From these data, it is clear that the number of cases were at least doubling each year until 1984, but since then, the rate of increase has decreased to about 50 percent per year. The exact meaning of this is not clear.
In discussing this epidemic, it is essential to remember that AIDS is only one part of the spectrum of this illness. The process starts with infection by the agent causing AIDS known as the human immunodeficiency virus or the HIV. The first stage of this infection is without symptoms, and many infected people will be unaware of it. As far as is known, asymptomatic infected people are capable of transmitting HIV.
A second aspect is known as AIDS Related Complex, or ARC. This is a loose collection of symptoms including weight loss and fever. Finally, there is AIDS, which is defined as an infection with the HIV and a secondary infection, such as an infection with other organisms, most often Penumocystis carinii pneumonia, a malignancy known as Kaposi's sarcoma, dementia (HIV attacks neurons), or "wasting" syndrome.
One issue is how many asymptomatic infected persons will develop ARC or AIDS. It now seems clear that 20 to 30 percent will develop AIDS in a five-year period. A recent study in San Francisco indicates that in a six-year period, 30 percent of infected men developed AIDS and an additional 46 percent developed ARC. The question is what will happen in seven, eight, or ten years.
Scientific advances
An important scientific issue is that of vaccines. There are a number of possible approaches and all of them are under study. The first human trials of a candidate vaccine will begin shortly, and other vaccines are in development. A successful vaccine must be capable of generating neutralizing antibodies that will prevent the virus from entering the cell and probably also stimulate cellular immunity as well. Furthermore, it must do so without risk of
...
Read Full Article
|
