HIV infection and AIDS: epidemiology

Source (reservoir) of the human immunodeficiency virus

Source of HIV infection is HIV-infected people at any stage of the disease, regardless of the presence or absence of clinical manifestations of the disease, including during incubation.

Mechanisms, ways and factors of HIV transmission

The main mechanism of transmission is contact. There are natural, contributing to the persistence of HIV infection in nature and artificial transmission routes. To natural ways of transfer carry sexual (at sexual contacts) and vertical (from the infected mother to the child during pregnancy, sorts or at thoracal feeding).

Artificial (artificially) transmission pathway - parenteral - is realized when the virus enters the bloodstream under various manipulations associated with a violation of the integrity of the mucous membranes and skin.

Factors influencing the likelihood of infection of the sexual partner of HIV include the virus titer at the source of the infection: the presence of various diseases in the recipient; intensity of contact.

The modern epidemiology of HIV infection excludes the existence of aerosol, fecal-oral and transmissible transmission mechanisms of the pathogen.

The susceptibility of a person to HIV is almost one hundred percent. The factor of immunity to HIV infection may be the absence of specific specific receptors. At present, genes (CCR5, CCR2 and SDF1) are isolated that control the synthesis of molecules involved in the penetration of HIV into host cells. Thus, people who have a homozygous genotype for these genes are immune to HIV infection through sexual contact; Persons with a heterozygous genotype are less stable. It was found that people who are in long-term contact with HIV-infected and uninfected people have a mutation in the gene responsible for the expression of the CCR5 coreceptor on the surface of lymphocytes (it is found only in 1% of Europeans). However, this feature is not associated with immunity to HIV during blood transfusions or when intravenous psychoactive substances are introduced.

HIV infection is ubiquitous. Currently, it is officially registered in almost all countries of the world. At the same time, the prevalence of HIV infection is extremely uneven in different regions, different age, social and professional groups. The largest number of people living with HIV live in Central Africa (to the south of the Sahara Desert) and in the Caribbean islands. An important indicator is the increase in the number of new cases. In the early 80-ies of the XX century, the maximum number of cases of HIV infection was recorded in Central Africa and the United States. And by the end of 2000 all continents were already involved in the epidemic. In Ukraine, HIV infection has been registered since 1985 initially among foreigners, mostly from Africa, and since 1987 - among citizens of the USSR.

Until the mid-1990s, the main way of HIV transmission in Ukraine was considered sexual. This determined the originality of the epidemic process of infection. Since the second half of 1996, there has been a shift in the leading route of transmission. The first place was taken by "injecting" infection, usually among drug addicts who practice parenteral administration of psychoactive substances. In recent years, the importance of heterosexual transmission of HIV infection has been increasing. This is evidenced not only by the increase in the number of infected (the main risk factor for which is heterosexual contact), but also the increase in the proportion of infected women. As a consequence, the likelihood of HIV transmission from mother to child is increased.