Human immunodeficiency virus is DNA-containing, belongs to the genus Lentivirus of the family Retroviridae. Two types are distinguished: HIV-1 is the main causative agent of HIV infection, the cause of the pandemic, the development of AIDS. HIV-2 is a low-prevalence type, found mainly in West Africa. HIV is an unstable virus, quickly dies outside the host’s body, is sensitive to temperature (reduces infectious properties at 56 ° C, dies in 10 minutes when heated to 70-80 ° C). It is well preserved in blood and its preparations prepared for transfusion. The antigenic structure of the virus is very variable.
The reservoir and source of HIV infection is a person: an AIDS sufferer and a carrier. No natural reservoirs of HIV-1 have been identified; it is believed that the natural host in nature is wild chimpanzees. HIV-2 is carried by African monkeys. Susceptibility to HIV in other animal species has not been noted. The virus is found in high concentrations in blood, semen, vaginal gland secretion, and menstrual secretions. It can be excreted from women’s milk, saliva, tear secretion and liquor, but these biological fluids pose a lower epidemiologic risk.
The probability of HIV transmission increases in the presence of skin and mucous membrane injuries (trauma, abrasions, cervical erosion, stomatitis, paradontosis, etc.). ) HIV is transmitted by hemocontact and biocontact mechanism naturally (through sexual contacts and vertically: from mother to child) and artificially (mainly realized by hemopercutaneous mechanism of transmission: during transfusions, parenteral injections of substances, traumatic medical procedures).
The risk of HIV infection in a single contact with a carrier is low, while regular sexual contacts with an infected person significantly increase it. Vertical transmission from a sick mother to her child is possible both in the intrauterine period (through defects in the placental barrier) and in labor, when the child comes into contact with the mother’s blood. In rare cases, postnatal transmission with breast milk is recorded. The incidence among children of infected mothers reaches 25-30%.
Parenteral infection occurs through injections with needles contaminated with the blood of HIV-infected persons, hemotransfusion of contaminated blood, non-sterile medical manipulations (piercing, tattoos, medical and dental procedures performed with instruments without proper treatment). HIV is not transmitted by household contact. Human susceptibility to HIV infection is high. The development of AIDS in persons over 35 years of age, as a rule, occurs in a shorter period of time from the moment of infection. In some cases, immunity to HIV is noted, which is associated with specific immunoglobulin A present on the mucous membranes of the genital organs.