The science that studies the sources of infection, the mechanism and ways of transmission of infection, as well as ways to prevent infectious diseases, is called epidemiology. Knowing about the source of infection, the way of its transmission, the duration of the latent (incubation) period, it is necessary to obtain important information for making a diagnosis and to outline a plan for organizing preventive and anti-epidemic measures.

Knowing the mechanisms and ways of transmission of some infectious diseases, you can protect yourself from infection with infectious diseases by taking personal preventive measures.


In intestinal infectious diseases, infection occurs through the oral cavity, more often with food and water. Pathogens from patients and bacterial carriers enter the external environment together with feces or vomit, sometimes with urine. Microbes of intestinal infections can remain viable for a long time in the soil, in water, as well as on all kinds of objects (wooden handles, furniture). They withstand the effects of low temperatures, survive longer in a humid environment. They multiply rapidly in dairy products, as well as in minced meat, jelly, jelly, in water (especially in summer). In some intestinal infections, primarily in cholera, the main, in fact, the only way of transmission is by water. The transmission waterway may be the main one for dysentery caused by Flexner’s shigella. There is no doubt that in this case, the water is polluted with excrement when sewage from toilets, sewers, etc. enters reservoirs.The degree of water pollution is especially high in the lower reaches of large rivers in regions with a hot climate. The transfer of the pathogen to food is carried out through the dirty hands of food workers, as well as by flies. Especially dangerous is the contamination of food products that are not subjected to heat treatment. Flies, feeding on feces, absorb a huge number of microbes. Almost 10 million microbes are placed on the fly’s body. Flying into the kitchen, into houses, into canteens, flies land on food. At one time alone, the fly is able to isolate up to 30 thousand dysentery microorganisms from the intestines. People who do not follow the rules of personal hygiene are most susceptible to infectious diseases, and they themselves are the distributors of intestinal infections. Intestinal infections, in addition to the above, include typhoid fever and paratyphs A and B, viral hepatitis A and B, etc.


Respiratory tract infections are the most common, the most widespread diseases. They are characterized by an airborne method of distribution with the localization of the pathogen in the respiratory tract. The transmission of pathogenic microorganisms occurs when talking, sneezing, coughing, when staying together with the sick in a close room. This group of airborne droplet infections primarily includes influenza and other acute respiratory diseases (ARI, ARVI). The airborne route of transmission is the main one for most other infectious diseases: diphtheria, meningococcal infection, sore throat, measles, rubella, etc. In these diseases, pathogens appear in the air together with droplets of saliva or mucus. Their maximum concentration is observed at a distance of 2-3 m from the patient. Tiny droplets of saliva can stay near the patient for a long time. Large drops of saliva, including pathogens, settle quickly enough, dry up and form microscopic nucleoli. With the dust, they again soar into the air and with its flows move further to other rooms. When ingesting these substrates, infection occurs. In some infectious diseases, the leading route of transmission is not airborne, but airborne dust: with ornithosis, hemorrhagic fever with renal syndrome (HFRS), etc.


Blood-borne vector-borne infections. The source of infection is a sick person or a sick animal. Arthropods (lice, fleas, ticks, etc.) are considered carriers of pathogens, in which microorganisms multiply in the body. Microbes enter the body when they get into a wound from a bite or combing of a pathogen contained in saliva or in the crushed body of an insect. Such blood infections are called vector-borne, their pathogens are carried by living organisms, they include typhus, malaria, plague, tick-borne borreliosis, etc.

Non-transmissive blood infections. The infection is transmitted by contact with the blood of an infected person. Transmission routes can be both natural and artificial. Natural transmission routes:

Sexual: from the mother to the fetus (infection during pregnancy and childbirth), from the mother’s infant (when breastfeeding);

Household: when implementing a blood-contact mechanism through shaving devices, toothbrushes, etc.;

Artificial: through damaged skin, mucous membranes during therapeutic and diagnostic manipulations: injections, operations, blood transfusions, endoscopic examinations, etc.;

Blood contact: with viral hepatitis B, C and D, with AIDS.


The source of infection of this group of diseases can be both people (erysipelas) and animals (anthrax, etc.). A typical feature of these diseases is the introduction of the pathogen in places of violation of the integrity of the skin in the form of scuffs, abrasions, wounds, burns. The causative agents of individual infections can persist in the soil for a long period (tetanus). Infection in such cases occurs as a result of contamination of the wound with earth.

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