As recently as a decade ago it was widely believed that infectious disease was no longer much of a threat in the developed world. The confidence was shattered in the early 1980's by the advent of AIDS. Here was a devastating disease caused by a class of infectious agents - retroviruses - that had first been found in human beings only a few years before. In spite of the startling nature of the epidemic, science responded quickly. In the two years from mid-1982 to mid-1984 the outlines of the epidemic were clarified, a new virus - the human immunodeficiency virus (HIV) - was isolated and shown to cause the diease, a blood test was formulated and the virus's targets in the body were established.
Following that initial burst, progress has been steady, albeit slower. Yet in some respects the virus has outpaced science. No cure or vaccine is yet available, and the epidemic continues to spread; disease-causing retroviruses will be among the human population for a long time. In view of that prospect, it is essential to ask where we stand in relation to AIDS.
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Today AIDS has become a major cause of morbidity and mortality in the world. The discovery of the pandemic, the enumeration of the varied manifestations of HIV infection and the analysis of the circumstances that made it possible for such and infecction to spread have been missions assigned to epidemiology : the study of the occurence and distribution of disease as well as its control in a given population. Epidemiologists monitor mortality and morbidity rates asociated with HIV infection and AIDS; they also make predictions of likely changes in HIV infection rates in the course of time.Figure 1 represents the global distribution of AIDS. Figure 2 shows the percentage by continents of AIDS cases globally.
Indeed, it has become the leading cause of death in the country among people with hemophilia and users of illegal intravenous (IV) drugs. Most of those affected in the near future will be either homosexual men or IV drug users. Yet, given the fact that the virus is transmitted through sexual contact , through the traces of blood in needles and other drug paraphenlia and from mother to newborn infant, one can envision many possible chains of infection, which leave no segment of the world population completely unaffected by the threat of AIDS.
For current global situation of the HIV/AIDS pandemic provided by World Health Organization (WHO)
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Etiology and Pathogenesis of HIV
The causative agent of AIDS, human immunodeficiency virus (HIV) is a retrovirus, so called because this ssRNA virus contains a pol gene that codes for a reverse transcriptase. HIV infects cells bearing the CD4 antigen, including T helper cells (Th), monocytes and dentritic cells. The CD4 molecule acts as a binding site for the gp120 envelop glycoprotein of the virus. Productive replication and cell destruction does not occur until the T helper cell is activated. T cell activation is greatly enhanced not only in attempts to respond to HIV antigens, but also as a result of the Opportunistic Infections>secondary microbial infections seen in patients. As a result of the decreased numbers of CD4-positive T helper cells and defects in antigen presentation, together with other feactors such as the production of virus coded immunosuppressive molecules, there are depressed immune responses. The immunosupression is permanenet, the patient remains infectious, and the virus persists in the bocy. THe evenual mortality due to opportunistic infections, tumors etc., approaches 100%.
Symptoms of HIV Infection and Opportunistic Infections Related to AIDS
For the majority of patients the first sign that something is amiss in the immune system is the development of chronically swollen lymph nodes. Withe the appearance of this chronic lymphdenopathy a patient moves to stage 2. The cause of lymphadenopathy is relatively straight forward. The ongoing presence of HIV overstimulates B cells, which are abundant in the lymph nodes, and keeps them in a state of chronic activation. The flood of antibodies produced as aresult of such activation includes some antibodies that combat current infections or recurrences of past infections. In general, however, the hy[eractivity is not beneficial. The activation of large number of B cells diminishes the number of resting cells that can differenc--tiate to produce antibodies inresponse to new pathogens or to inoculation with vaccines. As the HIV infection progresses from stage 2 to stage 6, the patient's immune system worsens. This systemic immune defficiency is what allows opportunistic diseases to occur. Opportunistic diseases are usually caused by normal flora of the human body(i.e. Candida albicans) and immunosupressed organisms(i.e. Coccidiodes immitus). For more infomation on opportunistic diseases of AIDS, click on any one of the following list:
Laboratory tests for HIV infection depend on the demostration of specific antibodies. Initially an
ELIZA test is carried out. A positive result is confirmed by either western blotting, radioimmunoassay or immunofluorencence testing. This is done because the ELIZA test very occasionally gives a false positive report, and to elimiate possible errors in the clinic or laboratory. Diagnosis of HIV infection in newborn infants is a problem. If IgG antibodies are present they are presumably of maternal origin, and tests for virus specific IgM antibodies, which would signify inutero infection are not yet available. Hopefully, reliable tests for HIV antigens or nucleic sequences will soon be developed.
For more information on voluntary HIV counciling and testing counciling and testing
The best way to combat any disease is to prevent it. The main effort in the prevention of HIV infection concerns mass public education programmes. These involve inducements to change sexual behaviour, particularly reduction in promiscuous behaviour, and the use of barrier contraceptives (condoms). All blood donors are tested for antiboies and they are discouraged from volunteering if they belong to high risk HIV groups. Heat treatment of blood is done to minimize the HIV in blood. HIV is also inactivated by hypochlodites to as low as 1 in 10,000 ppm.
Vaccination is usually the simplest, safest and most effective form of prevention. Thus vaccine development has been a top priority of AIDS research since HIV was conclusively shown to be the cause of the diease in 1984. Yet in spite of the millions of dollars and hundreds of scientsts devoted to vaccine research, no effective vaccine has been developed to prevent HIV infection. Several vaccines are currently being tested in humans. It is too early to pronounce on their performance, but most investigators are not optimistic.
For some of the current literatures on GP160 vaccine and HIV
An AIDS treatment newsgroup
An Experimental Treatment for AIDS Bulletin
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Treatment of HIV Infection
The opportunistic infections associated with AIDS are treated in appropriet way depending on the type of infection. So far azidothymidine (AZT) and other alternative drugs such as DDI have been shown to prolong the lives of certain AIDS patients. 
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