Acquired Immune Deficiency Syndrome(acronym for acquired immune deficiency syndrome)
The gravest of the sexually transmitted diseases, or STDs. It is caused by the human immunodeficiency virus (HIV), now known to be a retrovirus, an organism first identified 1983. HIV is transmitted in body fluids, mainly blood and genital secretions.
Sexual transmission of the AIDS virus endangers heterosexual men and women as well as high-risk groups, such as homosexual and bisexual men, prostitutes, intravenous drug-users sharing needles, and hemophiliacs and other patients treated with contaminated blood products. The virus itself is not selective: worldwide, heterosexual activity accounts for three-quarters of all HIV infections. The virus has a short life outside the body, which makes transmission of the infection by methods other than sexual contact, blood transfusion, and shared syringes extremely unlikely.
The effect of the virus in those who become ill is the devastation of the immune system, leaving the victim susceptible to diseases that would not otherwise develop. Diagnosis of AIDS is based on the appearance of rare tumors or opportunistic infections in unexpected candidates. Pneumocystis carinii pneumonia, for instance, normally seen only in the malnourished or those whose immune systems have been deliberately suppressed, is common among AIDS victims and, for them, a leading cause of death. However, many people who have HIV in their blood are not ill; in fact, it was hitherto thought that during the delay between infection with HIV and the development of AIDS the virus lay dormant. But results from 1995 research into the reproduction rate of HIV are likely to alter the approach to AIDS management; US researchers now estimate that HIV reproduces at a rate of a billion viruses a day, even in individuals with no symptoms, but is held at bay by the immune system producing enough white blood cells (CD4 cells) to destroy them. Gradually, the virus mutates so much that the immune system is unable to continue to counteract; people with advanced AIDS have virtually no CD4 cells remaining. These results indicate the importance of treating HIV-positive individuals before symptoms develop, rather than delaying treatment till AIDS onset.
In the West the time-lag between infection with HIV and the development of AIDS seems to be about 10 years, but progression is far more rapid in developing countries. Some AIDS victims die within a few months of the outbreak of symptoms, some survive for several years; roughly 50% are dead within three years. There is no cure for the disease and the four antivirals currently in use against AIDS have not lived up to expectations. Trials began 1994 using a new AIDS drug called 3TC in conjunction with zidovudine (formerly AZT). Though individually the drugs produce little effect, together the 1995 results are indicating some success; the levels of virus in the blood were 10 times lower than at the beginning of the trial. Treatment of opportunistic infections extended the average length of survival with AIDS (in Western countries) from about 11 months 1985 to 23 months 1994.
the spread of AIDS
At the beginning of 1995, the official tally of AIDS cases worldwide exceeded one million for the first time. As of 31 Dec 1994, 1,025,073 cumulative AIDS cases in adults and children had been reported to the World Health Organization (WHO) by 192 national governments since the onset of the pandemic. This represents a 20% increase from the 851,628 cases reported to 31 Dec 1993. Of the total number of AIDS cases reported, 39% were in the US, 34% in Africa, 12.5% in Europe, 12% in the Americas, and 20% in Asia. According to reports released Jan 1995 by researchers from the US Centers for Disease Control and Prevention, in 1993 AIDS for the first time became the country's leading cause of death among all people aged between 25 and 44.
Allowing for under-diagnosis, incomplete reporting, and reporting delay, and based on the available data on HIV infections around the world, it is estimated that over 4.5 million AIDS cases in adults and children have occurred worldwide since the pandemic began. WHO estimate that of these cases, which include active AIDS cases and people who have died of AIDS, not HIV infections, more than 70% were in Africa, with about 9% in the US, 9% in the rest of the Americas, 6% in Asia, and 4% in Europe.
By mid-1994 WHO estimate of the number of HIV infections worldwide was 16 million, a figure likely to rise to 40 million by the year 2000. Worst affected is sub-Saharan Africa (where the virus probably originated) with about 9 million people believed to be HIV-positive. A large study in rural Uganda 1993 showed more than 50% of deaths in the villages to be HIV-related. In the 13–44 age group the proportion rose to more than 80%. Figures are also increasing in South America, and the new cases of HIV in Asia are expected to exceed those in Africa by 1997. In comparison the rate of spread is much slower in North Africa and the Middle East, possibly due to religious and cultural reasons (in countries with mixed populations the incidence of HIV infection in Muslims is about half that in non-Muslims).
The cumulative direct and indirect costs of HIV and AIDS in the 1980s have been conservatively estimated at $240 billion. The global cost—direct and indirect—of HIV and AIDS by the year 2000 could be as high as $500 billion a year —equivalent to more than 2% of global GDP.
The AIDS virus is thought to have originated in Africa, where the disease is most widespread. In the United States, where there have been more than a quarter of a million AIDS by the beginning of 1994, there is a worrying link with tuberculosis, a disease undergoing a marked resurgence, particularly in inner city ares.
A serious (often fatal) disease of the immune system transmitted through blood products especially by sexual contact or contaminated needles; Also called: acquired immune deficiency syndrome.
A disease of the human immune system that is characterized cytologically especially by reduction in the numbers of CD4-bearing helper T cells to 20 percent or less of normal thereby rendering the subject highly vulnerable to life-threatening conditions (as Pneumocystis carinii pneumonia) and to some (as Kaposi's sarcoma) that become life-threatening and that is caused by infection with HIV commonly transmitted in infected blood especially during illicit intravenous drug use and in bodily secretions (as semen) during sexual intercourse