All iLive content is medically reviewed or fact checked to ensure as much factual accuracy as possible.
We have strict sourcing guidelines and only link to reputable media sites, academic research institutions and, whenever possible, medically peer reviewed studies. Note that the numbers in parentheses ([1], [2], etc.) are clickable links to these studies.
If you feel that any of our content is inaccurate, out-of-date, or otherwise questionable, please select it and press Ctrl + Enter.
HIV infection and AIDS - Epidemiology
Medical expert of the article
Last reviewed: 04.07.2025
Source (reservoir) of human immunodeficiency virus
The 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 the incubation period.
Mechanisms, routes and factors of HIV transmission
The main mechanism of transmission of the infection is contact. There are natural, contributing to the preservation of HIV infection in nature, and artificial transmission routes. Natural transmission routes include sexual (during sexual contact) and vertical (from an infected mother to a child during pregnancy, childbirth or breastfeeding).
The artificial (artificial) route of transmission - parenteral - is realized when the virus enters the blood during various manipulations associated with a violation of the integrity of the mucous membranes and skin.
Factors influencing the likelihood of a sexual partner becoming infected with HIV include the titer of the virus at the source of infection; the presence of various diseases in the recipient; and the intensity of contact.
Modern epidemiology of HIV infection excludes the existence of aerosol, feco-oral and transmissible mechanisms of transmission of the pathogen.
Human susceptibility to HIV is almost 100%. The absence of certain specific receptors may be a factor in immunity to HIV infection. Currently, genes (CCR5, CCR2 and SDF1) are identified that control the synthesis of molecules involved in the penetration of HIV into host cells. Thus, people with a homozygous genotype for these genes are resistant to sexually transmitted HIV infection; people with a heterozygous genotype are less resistant. It has been established that people who have had long-term contact with HIV-infected people and who have not become infected have a mutation in the gene responsible for the expression of the CCR5 coreceptor on the surface of lymphocytes (it is found in only 1% of Europeans). However, this feature is not associated with immunity to HIV during blood transfusions or intravenous administration of psychoactive substances.
HIV infection is widespread. 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 HIV-infected people live in Central Africa (south of the Sahara Desert) and the Caribbean Islands. An important indicator is considered to be the increase in the number of new cases. In the early 80s of the 20th century, the maximum number of HIV cases was registered in Central Africa and the USA. And by the end of 2000, all continents were involved in the epidemic. In Ukraine, HIV infection has been registered since 1985, initially among foreigners, mainly people from Africa, and since 1987 - among citizens of the USSR.
Until the mid-1990s, sexual intercourse was considered the main route of HIV transmission in Ukraine. This determined the peculiarity of the epidemic process of infection. Since the second half of 1996, the leading route of infection transmission has changed. The first place was taken by "injection" infection, usually among drug addicts who practice parenteral administration of psychoactive substances. In recent years, the significance of the heterosexual route of HIV transmission has increased. This is evidenced not only by the increase in the number of infected people (the main risk factor for whom is heterosexual contacts), but also by the growth in the proportion of infected women. As a result, the probability of HIV transmission from mother to child increases.