The world around us is inhabited by a huge number of microorganisms invisible to the human eye. Some of them do not pose any danger, while others are capable of causing various diseases. What ways and means of transmission of infection exist is a question that deserves attention.
Infection: mechanism and route of transmission. Definitions of terms
In a science such as epidemiology, the concept of "infection" is used. This term refers to the danger of infection of a plant, animal or human body with various pathogenic pathogens. These include protozoa, bacteria, viruses, etc. Infections are transmitted according to certain mechanisms. They are understood as a set of specific ways of moving pathogens from a source to a susceptible organism.
Experts identify 4 transmission mechanisms:
- fecal-oral;
- aerosol-aerogenic;
- transmissive;
- blood contact.
Each mechanism is implemented in different ways (methods). This term refers to the factors that providepenetration of an infection into a susceptible organism under certain conditions.
Fecal-oral transmission pathways
Infections characteristic of this transmission mechanism are called intestinal infections. The pathogen lives in the digestive system of the host. Microorganisms enter the environment with faeces. In a new organism, pathogens penetrate in various ways. Here are ways to transmit intestinal infection:
- water (when drinking contaminated water);
- food (through eggs, meat, fish, milk, contaminated vegetables, fruits and berries);
- contact household (through various household items).
Microorganisms are introduced into the water due to the direct ingress of feces or contaminated soil into it. With food and contact-household transmission, food and household items are often infected after a sick person, who serves as a source of infection, touches them. Flies play an important role in the transmission of pathogens. Pathogenic microorganisms get on the paws of insects from feces.
An example of a fecal-oral infection
One of the well-known human diseases is dysentery. This is an ailment, which is characterized by syndromes of damage to the gastrointestinal tract and general infectious intoxication. The disease occurs due to dysentery sticks belonging to the genus Shigella. Ways of infection transmission - water, food and contact-household.
Currently, dysentery is diagnosed inisolated cases. Infection occurs:
- due to the use of water from the river, wells, pumps, which are in poor sanitary condition;
- eating insufficiently processed food (dirty, raw).
Outbreaks are also possible - group diseases. Water epidemics are caused by violations of decentralized and centralized water supply. Contact-household outbreaks often occur in preschool institutions due to violation of the anti-epidemic regime (for example, due to poor-quality disinfection measures).
Routes of transmission of infection in the aerosol-aerogenic mechanism
This transmission mechanism has several names. In the specialized literature, you can find such names as aspiration, aerosol, drip. After analyzing them, one can understand that the aerosol-aerogenic mechanism of transmission is characterized by the localization of the pathogen in the organs of the respiratory system.
Microorganisms can be transmitted in the following ways(s):
- Airborne. The causative agent is released when coughing, sneezing, talking. Droplets of infected mucus enter the environment, and then with air penetrate the bodies of he althy people.
- Airborne dust. With this method of transmission, a he althy person becomes infected after ingestion of airborne dust particles containing the infection.
Examples of diseases with aerosol-airborne mechanism of transmission
The flu iscommon viral disease. The main mode of transmission of infection is airborne. When the disease affects the upper respiratory tract. When the virus enters the body of a he althy person, symptoms such as weakness, headaches, muscle and joint pain appear. The body temperature rises. After some time, patients begin to complain of nasal congestion, sore throat, dry cough.
Air-dust transmission is characteristic of scarlet fever, a streptococcal infection characterized by a punctate rash, tonsillitis and signs of general intoxication. In case of illness, pathogens are excreted from the body of a sick person with sputum, pus. They are very resistant to environmental influences. This explains the possibility of infection through air and dust.
Routes of transmission of infection with a transmissible mechanism
For the transmission mechanism of transmission is characterized by the habitation of pathogens in the blood of the host. In a he althy body, the infection enters due to arthropods (fleas, lice, mosquitoes, ticks, flies). Carriers are divided into specific and non-specific. The first group includes such arthropods that carry certain diseases. For example, specific carriers of malaria are mosquitoes, typhus - lice. The second group includes flies that carry acute intestinal infections, typhoid fever, hepatitis A.
The transmission mechanism can be transmitted:
- anthroponosis (reservoir and source of infection is onlyperson);
- zoonoses (animals act as a reservoir and source of infection);
- anthropozoonoses (both animals and humans can be the source of infection).
Examples of transmissible diseases
One of the vector-borne infections is malaria. This is an anroponous disease caused by protozoa of the genus Plasmodium. Pathogenic microorganisms are transmitted from sick people to he althy people through mosquitoes belonging to the genus Anopheles. The new host becomes infectious only when the sexual forms of the pathogen - gametocytes - appear in the blood. For example, with tropical malaria, this occurs about a week after the onset of parasitemia and continues throughout the year.
Another example of a transmissible disease is plague. The causative agent is Yersinia pestis (a non-motile rod-shaped bacterium). The source of infection in nature is rodents, and the carrier is fleas. In these blood-sucking insects, after eating infected blood, the plague microbe begins to multiply in the digestive system. Pathogens accumulate and fill the lumen of the digestive tube. With subsequent bites of animals or people, fleas regurgitate pathogens and thereby provide infection.
Transmission pathways inherent in the blood contact mechanism
Blood contact mechanism of transmission is characteristic of many infections: bacterial, fungal, viral, protozoal, parasitic. Pathogens enter the body in a variety of ways. By thisreason, the following methods of transmission of infection are distinguished:
- vertical;
- parenteral;
- transplant;
- sexual.
The vertical mode of transmission of infection is explained by the penetration of the pathogen into the body of the fetus from the body of a pregnant woman through the placenta. The parenteral method is characterized by medical manipulations. For example, in some cases, people become infected in the dental office when the doctor uses non-sterile instruments. The transplantation method of transmission of infection is realized during the transplantation of internal organs. The latter path is inherent in diseases transmitted through sexual intercourse.
In addition, it is possible to single out the contact method of infection transmission. With it, infection occurs through direct contact with a source of pathogens and introduction to the surface of the mucous membranes and skin (for example, with scabies)
Example of a disease with a blood-borne transmission mechanism
A pressing medical and social problem lies in the fact that many people do not know or ignore the ways of transmitting sexual infections, do not protect themselves during casual relationships. That is why STDs are so often diagnosed by doctors.
An example of an infection with a blood-borne transmission mechanism is HIV. This disease affects the immune system. It is gradually destroyed until the formation of AIDS (acquired immunodeficiency syndrome). The causative agent is a virus from the retrovirus family. The patient is the source of infection.man.
Sexual and vertical modes of transmission of infection are the main (natural) in this disease. An artificial transmission route (parenteral and transplantation) is also being actively implemented. With it, the virus penetrates through damaged skin and mucous membranes during medical diagnostic procedures, drug administration, and tattooing in non-sterile conditions.
Nosocomial infections
Nosocomial infections (HAIs) deserve special attention. This is a very serious problem. With nosocomial infections, people become infected when they enter a hospital or seek medical care. Nosocomial infections cause significant damage to he alth. In addition, they increase the duration of treatment and stay in a medical facility, cause complications, and sometimes even lead to death.
Methods of transmission in a he alth care setting are varied. Pathogens enter human organisms both by natural (fecal-oral, aerosol-aerogenic) and artificial (during invasive medical and diagnostic procedures) routes. Nosocomial infections occur not only due to non-compliance with the sanitary-hygienic and anti-epidemic regime, but also due to the emergence of microorganisms resistant to chemotherapy drugs, antibiotics and adverse environmental factors.
In conclusion, it is worth noting that for each disease, certain ways (methods) of transmission of infections are characteristic. Knowing how it goesinfection, you can prevent certain ailments (for example, avoiding dirty foods, avoiding casual sex, living a he althy lifestyle, and avoiding drugs).
