In June 1981, the centers for The Disease Control of the United States reported that five young homosexual men in the Los Angels area had contracted
Pneumocystis Carinii pneumonia( a kind of pneumonia that is particularly found in AIDS patient). 2 of the patients had died. This report signalled the begninning of an epidemic of a viral disease characterized by immunosuppression associated with opportunistic infection( an infection caused by a microrganism that does not normally produce disease in human; it occurs in persons with abnomality functioning immune system), secondary neoplasms( any abnormal growth of new tissue, benign or malignant) and neurologic mainfestation, which has come to be known as AIDS.
Though Aids was first discovered in U.S.A, AIDS has been reported from more than 163 countries around the world and an estimated 10 million people are infected worldwide. Worsestill, the pool of HIV- infected persons in Africa is large and expanding.
Studies in the U.S.A. have retentified five groups of adults at risk for developing AIDS. The case distribution in these groups are as follows: (1).
Homosexuals or bisexual males constitute the largest group, about 60% of the reported cases. This includes 5% who were intravenuous drug as well. (2).
Intravenous drug users with no previous history of homosexuality compose the next largest group, about 23% of all patients. (3). Hemophiliacs (the people who have inborn disease characterized by excesssive bleeding and occuring only in males) especially those who received factor VIII concentrate before 1985, about
1% of all patients. (4). Recipents of blood and blood components who are not hemophiliacs but who received tranfusions of HIV-infected whole blood components
(e.g. platelet, plasma) account for 2 %. (5). Other high risk groups: 86% of patients acquire disease through heterosexual contacts with members of other high risk groups. 80% of children with AIDS have a HIV-infected parents and suffer from transplacental or perinatal transmission.
Thus from the preceding discussion, it should be aparent that transmission of HIV occurs under conditions that facilitate exchange of blood fluids containing the virus-infected cells. Hence, the three major routes of transmission are sexual contact , parenteral routes( ie adminstration of a substance not through the digestive system) and the passage of the virus from infected mothers to their new borns where are mainly by three routes: in the womb by transplacental spread, during delivery through a infected birth canal, and after birth by ingestion of breast milk.
It is little doubt that AIDS is caused by HIV-I, a human type C retrovirus ( RNA virus the contains the enzyme, reverse transcriptase , to