Causes of HIV

The causes of HIV are a number of factors that lead to a person being infected with an immunodeficiency virus. The virus can enter the body only through the blood. At the same time there are a number of factors that facilitate infection. At the same time, there are many misconceptions about how the pathogen is transmitted. In just a couple of decades, HIV has become a major problem in global health. Therefore, knowing the causes of infection is important even for children.

Virus as a cause of immunodeficiency

The pathogen responsible for the HIV pandemic is the human immunodeficiency virus. This name is derived from its influence on the affected organism. Once in the bloodstream, the microorganism is attached to the cells of the immune system. To attach a virus, there must be CD4 receptors on the surface of the donor cell. In the human body, there are a number of cells: microglial cells, T-helpers, dendritic cells, macrophages, Langerhans cells, monocytes.

After attachment, the virus begins to multiply, new virus particles appear. The main problem is that the virus attacks exactly those cells that are designed to destroy it. With an increase in the number of copies, the immunity weakens, a person becomes vulnerable to many bacteria, viruses, fungi. Against the background of helpless barrier function, tumor cells emerge from under control, new growths appear.

The amount of virus in the blood is called viral load: the higher it is, the weaker the body. The causative agent of the disease is among the lentiviruses - this is a family of retroviruses with a long incubation period and prolonged development of the disease. HIV infection also proceeds slowly in several stages. The rate of viral RNA replication depends on its type.

During the production of new copies of the virus often mutates. Virtually every new genome is somehow different from the previous one. Scientists estimate that the virus is just over 10 years old. During this time, 2 main types of pathogen appeared, each of which is divided into subtypes and groups. The type of HIV-1 (SIV-1), when people talk about HIV without specifying the type, means this type of reason for the mass epidemic. SIV-2 is less common, it is mainly located in West Africa.

Type SIV-1 progresses faster and more contagious than SIV-2. But modern tests recognize both types, and antiretroviral therapy is active against SIV-1 and SIV-2. Ways of infection are the same for any strains of the pathogen.

Sources of infection

The virus can live and multiply only in the human body, most of it in the blood, where the greatest number of cells with CD4. But besides blood, the pathogen is found in all biological fluids. The concentration of virus particles in different fluids varies. Therefore, their epidemiological significance is different.

Sources of HIV infection are people who are sick or infected with the immunodeficiency virus. Transmission of the pathogen is possible through:

  • blood;
  • cervical and vaginal secretions;
  • pre-ejaculate and sperm;
  • breast milk.

Even a short unprotected sex can end up infecting a partner. In addition, the pathogen is in other biological fluids, but the viral load in them is either too small, or these fluids are not available for contact:

  • cerebrospinal fluid - cerebrospinal fluid;
  • saliva;
  • sweat;
  • tears;
  • urine.

Given that viruses do not survive outside the human body, the main source of the disease is infected. But for infection, you need not only an HIV-positive and HIV-negative person. For a "successful" penetration of a pathogen, a suitable situation is needed. The biological fluid of an infected person must enter the blood of the uninfected person.

Main modes of transmission

In addition to being infected and healthy, getting infected fluid into the bloodstream, there must be sufficient virus concentration in the infected fluid. For example, most of the virus is found in the blood and secretions of the genital organs - it is easier to get infected by contact with them. And saliva, sweat and tears contain a low concentration of the infectious agent, therefore the probability of infection with them is less.

There are two ways of penetration of the pathogen into the carrier: artificial and natural:

  1. Artificial. There is a view of the introduction of infection from the outside. These include medical procedures: blood transfusion, the use of donor sperm, tools without proper disinfection. Such cases were common in the early years of the pandemic, when transmission routes were poorly understood. Today, all donor material is being tested for hepatitis and HIV.
    Artificial methods of infection include invasive manipulations in beauty salons, tattooing. Using non-disposable syringes and needles when injecting drugs is one of the most common causes of HIV transmission.
  2. Natural. These include contact household and vertical path. Among the first, the most popular route of infection is sexual. Only small children are infected vertically. From an HIV-positive mother, an infant may be affected by an infection during gestation, childbirth, and breastfeeding.

Thus, the main ways of spreading HIV infection are sexual, transplacental and directly through the blood.

During intercourse

Eastern Europe (Ukraine, Russia, Belarus, Moldova) and Africa remain the only regions where HIV continues to progress. According to WHO estimates, most developed countries manage to annually reduce the percentage of new infections by an average of 5-10% per year. In the post-Soviet space, the main route of infection of the younger generation is unprotected promiscuous sex.

According to sociologists, the sexual way accounts for 60% of cases of infection. Only in Russia every hour from 4 to 6 people are infected in this way. Infection occurs in any form of unprotected sex: heterosexual and homosexual, oral, anal, vaginal. The risk group also includes people who practice BDSM without protection. When interrupted intercourse infection is also transmitted. To avoid the risk of infection, it is recommended to take an HIV test for couples together every six months. For occasional sexual intercourse, be sure to use a condom.

Through blood

The second factor in the frequency of infection is direct contact with the blood of an infected person. In this case, the blood must go directly into the bloodstream or through wounds on the mucous or skin. In the secretion of the genital organs there are also cells with CD4 receptors. Penetrating through the cell membrane, the virus can join them, and then get into the lymph flow. The greatest probability of a virus entering the blood is through transfusion of infected blood.

A pathogen in a needle or syringe can live up to 14 days at a moderate temperature. Therefore, the likelihood of transmission by injecting drug users is very high. Repeated use of syringes and needles containing HIV blood can enter the bloodstream of a healthy person during medical procedures. During transfusion of infected blood, the development of the infection is almost inevitable.

However, the doctors themselves are at risk. During operations, injections, or other invasive procedures, the medical staff runs the risk of injury. Through the blood, an infection can also be transmitted by contact with the mucous membrane, if there are microtraumas on it. The probability of infection depends on the viral load in a patient. For medical staff there is a list of actions to prevent infection. If the contact with the carrier’s blood did take place, chemoprophylaxis is prescribed in the first hours after the incident.

The ingestion of HIV-positive blood on intact skin does not lead to infection. On the surface of the skin there are no such cells to which the virus can join. The risk of infection increases if the skin has cracks or open wounds. It is also possible to get infected through blood in tattoo parlors, SPA-centers, dental offices, nail salons. Wherever the integrity of the skin or mucous membrane is violated, it is imperative to use disposable instruments or to follow that the rules of disinfection are observed.

From mother to child

According to the WHO, the probability of infection from an HIV-positive woman's child in different countries ranges from 15% to 45%. The risk of infection for the entire period from conception to breastfeeding is estimated at 30%. Of them:

  • from 5% are infected during gestation;
  • 10% - when breastfeeding;
  • 15% - during childbirth.

The risk of transmitting the pathogen during labor and lactation can be controlled. Delivery is recommended by cesarean section. Thus, the risk of damage to the mucous membranes and skin of the infant is much reduced. The probability of infection during feeding varies from 12% to 20%. To exclude such a transmission factor completely, the newborn is transferred to artificial feeding.

The risk of infection increases in utero if a woman smokes, uses alcohol or drugs. Bad habits increase the chance of violation of the integrity of the placenta at the cellular level. The use of antiretroviral therapy and symptomatic treatment for the mother significantly reduces the risks of HIV transmission to the infant at all stages of pregnancy and later in the care of the child.

Possible transmission routes

As we have found out, there is a category of biological fluids that is more likely to transmit a pathogen. At the same time, there are fluids that contain the virus, but in very low concentrations. Contact with substances such as sweat, urine, tears or saliva - refer only to probable routes of infection.


The oral route of infection includes all situations where the pathogen enters the oral cavity of a healthy person. The greatest chance of infection with:

  • visiting the dentist;
  • using someone else's toothbrush or floss;
  • piercing the tongue or lips with a non-sterile needle or other instruments.

These pathways are more likely because they are associated with injury to the mucous membrane. Intact oral mucosa is a good barrier to the virus. The pathogen concentration in the saliva of an infected person is very low, and, besides, in the saliva and the gastrointestinal tract of a healthy person there are enzymes that prevent the adherence of pathogenic particles to lymphocytes.

Kiss - refers to the probable ways of transmission, since a small risk of infection appears if the receiving person has a bleeding wound. In order for a healthy person to become infected during a kiss, according to scientists, you need to exchange two liters of saliva. Therefore, it is considered that when kissing, HIV does not go to a partner.

HIV in everyday life

On the surfaces of tissues and objects the virus lives from several minutes to 2 hours. Laboratory experiments have shown that after the infected liquid has dried, HIV is still active for up to 3 days. However, the study uses a virus concentration that is hundreds of times higher than the possible concentration in human blood. Therefore, the pathogen lives outside the human body for no more than five minutes.

The higher the ambient temperature, the faster it is neutralized. There are no reported cases of infection through the general use of household items. Following the rules of prevention, the family of an HIV-infected person may not worry about their own health.

The main rule for preventing transmission at home is general and personal hygiene. Infected particles can be transmitted through a razor, nail accessories or a toothbrush. That is, only those objects that are in contact with blood. Also in everyday life can be damage to the skin of a sick and healthy person. For infection, it is necessary that a sufficient amount of HIV-positive blood gets into the open wound of the healthy.

To protect HIV-negative family members, it is recommended that all scratches and wounds be treated with iodine or brilliant green and sealed with a plaster. The same should be done to the patient for injuries. The house should be regularly cleaned with disinfectants. The virus is not transmitted through shared use of the toilet and bathroom.

How HIV is not transmitted

Know the pathogen transmission paths for your own safety. But it is just as important to know the ways in which HIV is not transmitted. The virus absolutely does not pass from one person to another through hugs, by airborne droplets, with handshakes or other touches. Even getting an infected liquid on the whole skin is safe.

There is no risk in the general use of the bathroom, toilet, pool, bath.

The virus is also not transmitted through joint washing of clothes or clothes. First, it dies at temperatures above 60 degrees for 1-2 minutes. Secondly, even if the pathogen is on the fabric - there is very little of it for infection. And thirdly, HIV is killed by the action of disinfectants and soap solutions. With the patient, you can change clothes and linen after washing. His underwear and towel should be his own.

Deep kisses remain a topic for discussion. Although there are no cases of transmission of the pathogen by this route (not a single one), it is still referred to as unlikely transmission routes. HIV cannot be transmitted by insect bites; they are not carriers of a dangerous virus.

No infection is transmitted during joint study, work, walking, socializing or playing sports. There are no reported cases of infection when sneezing and coughing, as in the secretions there are not enough infecting particles. You can communicate with HIV-positive people as well as with everyone else without superstitious fear.

Are chances of getting sick

If a person is not at risk - does not engage in unprotected sex, does not use someone else's needles and syringes - the risk of infection is almost zero. To reduce this possibility to nothing, check the disinfection of instruments in beauty salons, tattoo parlors and medical offices. If you suspect direct contact with infected blood or sexual secretion - immediately take the test in the AIDS center. If specialists find your situation critical, they will prescribe chemoprophylaxis.

For people who have promiscuous sex or injecting drugs, the risk of infection is very high. These populations are the main distributors of HIV.

Regardless of whether you are at risk or not, take an HIV test every six months. And if an infection is suspected, the analysis should be taken at intervals of 1-36 months.

Article author:
Izvozchikova Nina Vladislavovna

Specialty: infectious diseases specialist, gastroenterologist, pulmonologist.

Total experience: 35 years.

Education: 1975-1982, 1MMI, San gig, high qualification, infectious diseases doctor.

Science degree: doctor of the highest category, PhD.


  1. Infectious diseases.
  2. Parasitic diseases.
  3. Emergency conditions.
  4. Hiv
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