Knowing how infectious diseases spread will be useful not only for self-education, but also in order to protect yourself and your loved ones from the disease in the event of a risk of infection.
Transmission of infection: stages and sources
The mechanism of transmission is the way in which a disease agent travels from an infected source to a susceptible organism. This process, of course, does not happen all at once. First, the pathogen must somehow be isolated from an infected source, then it stays in the environment or in an intermediary animal for a certain period of time, and only after that it enters a susceptible organism in a certain way.
Everything starts from the source. In epidemiology, it is generally accepted that only those objects in which natural habitat, reproduction, and then the release of pathogens through physiological processes are possible can be sources of infection. Infected people or animals are the sources of infection. The transmission mechanism is determined by how the disease is transmitted further.
Ways and mechanisms of infection
Infection transmission routes are called inanimate objects that are not the natural habitat of these microbes, but actively participate in their transmission. This is mainly air and water, household items, food and soil - sometimes they are mistakenly considered sources of infection. In the general case, depending on where the pathogen is initially concentrated and by what means it is released, the main mechanisms of infection transmission are distinguished: aerosol, contact, alimentary, transmission.
Infection development factors
Interaction between microbes and the human body always does not occur in isolation, but in a combination of certain factors. Not only the mechanisms and ways of transmission of the infection are important, but also the state of the immune system at the time of infection, the dose of the pathogen, the parameters of the external environment and how the pathogenic microbe entered the body.
Each type of pathogenic microorganisms chooses the most favorable place for itself in the host's body - one that will provide it with the possibility of successful life, as well as subsequent release into the environment and distribution. As for the penetration of the infection, it is curious that evolutionarily, each pathogen has its own, often the only, "entrance doors" fixed. These can be mucous membranes of both the respiratory and digestive systems, damaged skin and the genitourinary system. The disease will not develop if its causative agentwill enter the human body not through its own, but through "foreign", unusual gates.
It is also interesting that in order for a disease to occur, a certain number of its pathogens are required. The infectious dose for each pathogen is different.
Aerosol mechanism
This is the most common transmission mechanism. Sometimes it is also called respiratory, aspiration or aerogenic, but most often this method is called airborne. This name well characterizes how infectious agents are transmitted in this case. Initially, viruses or bacteria are concentrated in the mucous membranes of the respiratory tract, and when sneezing, coughing or talking, along with droplets of saliva and mucus, they are released into the surrounding air. After staying in it in the form of an aerosol for some time, pathogens, together with the flow of inhaled air, enter the susceptible organism. Moreover, if drops of a relatively large size quickly settle, then fine aerosols are able to remain active for a long time and move over considerable distances. It should be clarified that pathogens can be found not only in drops, but also in dust particles. This applies to those pathogens that are resistant to drying.
Alimentary (food) mechanism
In this case, in the infected organism, the infection is localized in the intestine and is released into the environment with waste products. Infection is carried out already through the mouth, as a rule, with infected products.food and water. The infection can get into them from dirty hands, through the consumption of meat and milk of infected animals, through insects. This route is better known as the fecal-oral mechanism of transmission of the infectious agent - also a rather "speaking" name.
Contact way
Another fairly common transmission mechanism. In this case, the causative agents of the disease can be on the skin, mucous membranes, wounds. Interestingly, these pathogens are highly sensitive to environmental conditions, so direct contact with infected tissues is necessary for infection. However, infection can also occur through various objects. These can be bacterial, viral, fungal infections, as well as parasitic diseases.
Private variants of the contact mechanism
Often, these ways of infection are generally separated into separate groups. But, strictly speaking, they are only special cases of the already described contact mechanism. We are talking about sexual, hemocontact and vertical routes of infection. The sexual route involves infection through contact of the mucous membranes of the organs of the genitourinary system. The blood-contact route is infection through the infected blood of a source, when it enters directly into the bloodstream of a he althy person. This can happen during a blood transfusion, for example, or during medical procedures associated with damage to the skin.integument or mucous membranes with non-sterile instruments. The vertical route is so named because this mechanism of transmission ensures that the pathogen passes from one generation to the next, when the disease is transmitted either through the placenta during pregnancy or at the time of delivery.
Transmissible infection mechanism
With this mechanism, the pathogen is in the blood of the source, and it is realized through insects, namely blood-sucking: mosquitoes and mosquitoes, lice, ticks, fleas. In this case, insects serve as living transmission factors. Moreover, in the body of some of them, there is simply an accumulation of pathogens, while in others, a cycle of their development and reproduction is carried out. It is logical that the degree of infection is directly proportional to the size of the insect population. Infection usually occurs directly during the bite, but there is a high probability of penetration of pathogens into damaged skin if the insect is crushed.
It must be said that the above classification of the mechanisms of transmission of infectious agents is to some extent conditional. So, some sources do not single out the transmission mechanism as a separate group, but consider it a variant of the hemocontact - blood route. The transmission of infection through syringes and other non-sterile medical instruments is sometimes also quite logically attributed to the transmission mechanism, as is the intrauterine route.
Examples of infectious diseases depending on the mechanisms of their transmission
The number of microorganisms onThe earth is in the millions. Bacteria, viruses, fungi - many of them are harmless, while others cause quite dangerous diseases. Sources, mechanisms and ways of transmission of infection in cases of different diseases are different. It is unlikely that it will be possible to list all of them, but the most common ones are worth knowing, as well as possible ways of infecting them with pathogens.
So, the following are transmitted by airborne droplets: influenza, scarlet fever and chicken pox, rubella and measles, as well as meningitis, tonsillitis, tuberculosis and others. As for the fecal-oral route, this is usually the mechanism of transmission of intestinal infections: cholera, dysentery, hepatitis A, etc. In the same way, poliomyelitis is transmitted. Diseases transmitted by contact are various skin infections, tetanus, venereal diseases, anthrax. Finally, malaria, typhus, plague, and encephalitis are transmitted by transmissible means - through the bites of bloodsucking insects. Of course, not everything is so simple, and many infectious diseases are transmitted through not one, but several mechanisms.
Prevention
Compliance with the simplest rules of personal hygiene is one of the simplest and most reliable means of protecting against infectious diseases, especially those transmitted by alimentary means. It is also impossible to neglect thorough washing and sufficient heat treatment of food. The worst enemies of the spread of diseases transmitted through the air are the ventilation of premises, the isolation of the sick,use of medical masks if contact with them is necessary. In order to prevent infection through the blood, it is necessary, as far as possible, to carefully choose medical institutions, tattoo parlors and beauty salons. Much has been said about the prevention of sexually transmitted infections. Well, and finally, it is impossible not to mention the strengthening of immunity in every possible way. It is easier to prevent a disease than to treat it later.
