It will be useful to know how the spread of infectious diseases occurs, not only for the purpose of self-education, but also in order to protect yourself and your family and friends from the disease in case of risk of infection.
Transmission of infection: stages and sources
The mechanism of transmission of infection is the way in which the causative agent of the disease gets from an infected source to a susceptible organism. This process, of course, does not occur simultaneously. First, the pathogen must somehow stand out from the infected source, then for a certain period of time it stays in the environment or in an intermediary animal, and only after that it enters a susceptible organism in a certain way.
It all starts with 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 can be sources of infection. Infected people or animals are sources of infection. The mechanism of transmission of infection is determined by the way the disease is transmitted further.
Ways and mechanisms of infection
The means of transmission of infection are objects of inanimate nature, which are not the natural habitat of these microbes, but are actively involved in their transmission. This is mainly air and water, household items, food and soil - sometimes they are mistakenly considered to be sources of infection. In the general case, depending on where the pathogen was originally concentrated and by which its release occurs, the main mechanisms of infection transmission are distinguished: aerosol, contact, alimentary, transmission.
Infection factors
The interaction between microbes and the human body always does not occur in isolation, but in the aggregate of certain factors. Not only the mechanisms and transmission pathways of the infection are important, but also the state at the time of infection of the immune system, the dose of the pathogen, the parameters of the external environment and how the pathogen entered the body.
Each type of pathogenic microorganism chooses the most favorable place for itself in the host organism - one that will provide it with the opportunity for successful life activity, as well as subsequent release into the environment and spread. As for the penetration of infection, it is curious that evolutionally, each pathogen has its own, often the only "entrance door". This can be the mucous membranes of both the respiratory and digestive systems, damaged skin and the genitourinary system. The disease will not develop if its pathogen enters the human body not through its own, but through "alien" gates unusual for it.
It is also interesting that in order for the disease to occur, a certain amount of its pathogens is required. The infectious dose for each pathogen is different.
Aerosol mechanism
This is the most common infection transmission mechanism. Sometimes it is also called respiratory, aspiration or aerogenic, but most often this method is called airborne. This name well describes how the causative agents of infection 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, droplets of saliva and mucus are released into the surrounding air. After staying in it in the form of an aerosol for some time, pathogens, along with a stream of inhaled air, enter the susceptible organism. Moreover, if drops of a relatively large size quickly settle, then finely dispersed aerosols are able to remain active for a long time and travel considerable distances. It must be clarified that pathogens can be found not only in drops, but also in dust particles. This applies to pathogens that are resistant to drying.
Alimentary (food) mechanism
In this case, in an infected body, the infection is localized in the intestine and is released into the environment with waste products. Infection is carried out through the mouth, usually with infected food and water. Infection in them can get from dirty hands, through the use of meat and milk of infected animals, through insects. This pathway is more commonly known as the faecal-oral mechanism of transmission of the causative agent of infection - also a fairly “talking" name.
Contact way
Another fairly common mechanism of transmission of infection. The causative agents of the disease can be on the skin, mucous membranes, wounds. It is interesting that these pathogens are highly sensitive to environmental conditions, therefore, for infection with them, direct contact directly with infected tissues is necessary. However, infection can also occur through various objects. It can be bacterial, viral, fungal infections, as well as parasitic diseases.
Private contact mechanism options
Often these infection paths are generally distinguished into separate groups. But, strictly speaking, they are only special cases of the contact mechanism already described. We are talking about sexual, blood contact and vertical routes of infection. Genital tract involves infection by contact of the mucous membranes of the genitourinary system. The blood contact path is infection through the infected blood of a source, when it enters directly into the bloodstream of a healthy person. This can happen during a blood transfusion, for example, or during medical procedures involving damage to the skin or mucous membranes with non-sterile instruments. The vertical path is so named because this mechanism of transmission provides the pathogen from one generation to another when the disease is transmitted either through the placenta during pregnancy or during delivery.
Transmission mechanism of infection
With this mechanism, the pathogen is in the blood of the source, and it is realized through insects, namely blood-sucking ones: 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, 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 in the process of a bite, but pathogens are likely to enter the damaged skin if the insect is crushed.
It must be said that the above classification of the mechanisms of transmission of pathogens of infections is to some extent conditional. So, some sources do not distinguish the transmission mechanism in a separate group, but consider it a variant of the blood-contact bloodstream. The transmission of infection through syringes and other non-sterile medical instruments is sometimes also quite logically attributed to the transmission mechanism, as well as the intrauterine route.
Examples of infectious diseases depending on their transmission mechanisms
The number of microorganisms on Earth is in the millions. Bacteria, viruses, fungi - many of them are harmless, while others cause quite dangerous diseases. Sources, mechanisms and transmission of infection in cases of different diseases are different. All of them are unlikely to be listed, but the most common ones should be known, as well as possible methods of infection with their pathogens.
So, the following are transmitted by airborne droplets: flu, scarlet fever and chicken pox, rubella and measles, as well as meningitis, tonsillitis, tuberculosis and others. As for fecal-oral, this is usually a mechanism for the transmission of intestinal infections: cholera, dysentery, hepatitis A, etc. Polio infection occurs in the same way. Contact-transmitted diseases include various skin infections, tetanus, sexually transmitted diseases, and anthrax. Finally, malaria, typhoid, plague, and encephalitis are transmitted in a transmissible way - 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 to protect against infectious diseases, especially transmitted through nutrition. Thorough washing and sufficient heat treatment of food products must also not be neglected. The worst enemies of the spread of airborne diseases are airing the rooms, isolating the sick, using medical masks if necessary to contact them. In order to prevent infection through blood, you need, as far as possible, to carefully choose medical institutions, tattoo parlors and beauty salons. A lot has already been said about the prevention of sexual infection. Well, and finally, we can not fail to mention all sorts of strengthening immunity. It is easier to prevent a disease than to treat it later.