This virus attacks to the immune system and leaves the vulnerable body to a big illnesses variety. These illnesses are usually caused by bacteria, fungi and very common viruses that ordinarily do not cause illness.

THE VIH has been found in the blood, sperm, saliva, tears, nervous textile, maternal milk, and secretions of the genital tract. Nevertheless it is proved that of these there are the blood, the sperm, the secretions of the genital tract, and the maternal milk those who transmit the infection to others. The transmission of the virus happens by means of the sexual contact including the anal, vaginal and oral sex; by means of the blood by means of transfusions or infected needle; and in pregnant women to the fetus, or on having given of sucking the baby. Other rarer transmission methods include the accidental prick with a needle, the artificial insemination, in which the transmission happens across the donated sperm, and the transplante of kidney, in which the transmitter is the donated kidney.

The infection is not transmitted by chance contact such as to embrace or to touch, not for such inanimate objects as seats of service or plates, not for mosquitoes. There are not transmitted the persons who donate blood (although it can be transmitted from the blood contaminated to the person who receives the transfusion). It is because of it therefore the blood banks analyze the donors and his blood. Neither is transmitted a person who, for example, donates a kidney for one transplant.

The AIDS is preceded by the infection VIH, which cannot produce symptoms even for 10 years before the person is diagnosed of AIDS. The sharp infection for VIH progresses across the time up to becoming an infection for asymptomatic VIH and then it advances ending up turning into AIDS or illness for VIH. In a study realized between 1977 until 1980 on bearers of the VIH, some of them were not showing any sign or symptoms of infection, while others only had the inflamed lymphatic nodules. It is suspected that all the persons infected by VIH, develop the AIDS after a certain time. This theory there is not proved definitely.

The historical high-risk groups were males homosexual or bisexual, addicted to drugs intravenous route that there were sharing the needles, sexual couples of those that are in the groups of high risk, you drink that they are born of mothers with VIH. But nowadays they move to the heterosexual sexual contacts and especially in adolescents. The infection of the VIH is increasing more rapid between the young people. One of the four infections in the USA happens between the young people younger than 22 years. In 1993, persons diagnosed 588 new cases of AIDS between from 13 to 19 years of age, and 3.911 new cases between those from 20 to 24 years of age. Because the infection can happen up to 10 years before being diagnosed like AIDS, this means that most of the persons became infected with the VIH during the adolescence or in the pre-adolescence.