A huge number of microorganisms, invisible to the human eye, live in the surrounding world. 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. Explanation of Terms
A science like epidemiology uses the concept of infection. 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 in accordance with certain mechanisms. By them is meant a set of specific ways of moving pathogens from a source to a susceptible organism.
Experts distinguish 4 mechanisms of transmission of infection:
- fecal-oral;
- aerosol aerogenic;
- transmissible;
- blood contact.
Each mechanism is implemented in different ways (ways). This term refers to factors that ensure the penetration of an infection into a susceptible organism under certain conditions.
Transmission pathways characteristic of the fecal-oral mechanism
Infections characteristic of this transmission mechanism are called intestinal infections. The causative agent lives in the digestive system of the host. Microorganisms enter the environment along with feces. Pathogens enter the new organism in various ways. Here are ways to transmit an intestinal infection:
- water (with the use of contaminated water);
- food (through eggs, meat, fish, milk, contaminated vegetables, fruits and berries);
- contact household (through various household items).
In water, microorganisms are due to direct contact with feces or contaminated soil. With food and contact-household transmission routes, food and household items are often infected after a sick person who serves as a source of infection touches them. An important role in the transmission of pathogens is played by flies. Pathogens enter the legs of insects from feces.
Fecal Oral Transmission Example
One of the known human diseases is dysentery. This is an ailment characterized by gastrointestinal tract syndromes and general infectious intoxication. The disease occurs due to dysenteric sticks belonging to the genus Shigella. Methods of transmission of infection - water, food and contact-household.
Currently, dysentery is diagnosed in isolated cases. Infection occurs:
- due to the use of water from the river, wells, columns, which are in unsatisfactory sanitary condition;
- eating insufficiently processed food (dirty, raw).
Outbreaks are also possible - group diseases. Water epidemics are caused by disruptions in decentralized and centralized water supply. Contact-outbreaks often occur in preschools due to a violation of the anti-epidemic regime (for example, due to poorly performed disinfection measures).
Ways of transmission of infection with 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, it can be understood that the aerosol-aerogenic transmission mechanism is characterized by the localization of the pathogen in the respiratory system.
Microorganisms can be transmitted in the following ways (ways):
- Airborne. The causative agent is excreted by coughing, sneezing, talking. Droplets of infected mucus enter the environment, and then with air penetrate into the bodies of healthy people.
- Dusty. With this transmission method, a healthy person becomes infected after particles of suspended dust containing the infection enter the body.
Examples of diseases with aerosol-aerogenic transmission mechanism
Influenza is a common viral disease. The main method of transmission is airborne. With an ailment, the upper respiratory tract is affected. When the virus enters the body of a healthy person, symptoms such as weakness, headaches, muscle and joint pain appear. Body temperature rises. After some time, patients begin to complain of nasal congestion, sore throat, dry cough.
An air-dust transmission method is characteristic of scarlet fever - a streptococcal infection characterized by a small-pointed rash, tonsillitis and signs of general intoxication. With the disease, pathogens are excreted from the body of a sick person with sputum, pus. They are very resistant to environmental factors. This explains the possibility of infection through air and dust.
Transmission routes for the transmission mechanism
The transmission mechanism of transmission is characterized by the presence of pathogens in the blood of the host. The infection gets into a healthy body thanks to arthropods (fleas, lice, mosquitoes, ticks, flies). Carriers are divided into specific and non-specific. The first group includes arthropods that carry certain diseases. For example, mosquitoes, typhus - lice are specific carriers of malaria. The second group includes flies that carry acute intestinal infections, typhoid fever, hepatitis A.
The transmission mechanism can be transmitted:
- anthroponosis (only a person serves as a reservoir and source of infection);
- zoonoses (animals act as a reservoir and source of infection);
- anthropozoonoses ( both animals and humans can be a source of infection ).
Transmissible diseases examples
One of the vector-borne infections is malaria. This is an anroponous disease caused by protozoa of the genus Plasmodium. Pathogens are transmitted from sick to healthy people through mosquitoes belonging to the genus Anopheles. A new host becomes contagious only when the sexually transmitted pathogen, gametocytes, appears in the blood. For example, with tropical malaria, this occurs about a week after the onset of parasitemia and lasts for a year.
Another example of a disease with a transmissible transmission mechanism is plague. The causative agent is Yersinia pestis (a motionless, stick-shaped bacterium). Rodents act as a source of infection in nature, and fleas act as a carrier. In these blood-sucking insects, after using infected blood in the digestive system, the plague microbe begins to multiply. Pathogens accumulate and fill the lumen of the digestive tube. With subsequent bites of animals or people, fleas spit pathogens and thereby provide infection.
Routes of transmission inherent in the blood contact mechanism
The hemocontact transmission mechanism is characteristic of many infections: bacterial, fungal, viral, protozoal, parasitic. Pathogens enter the body in many ways. For this reason, the following transmission methods are distinguished:
- vertical;
- parenteral;
- transplantation;
- sexual.
The vertical method of transmission of infection is explained by the penetration of the pathogen into the fetal body from the body of a pregnant woman through the placenta. For the parenteral method, medical manipulations are characteristic. 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 by transplantation of internal organs. The last way is inherent in diseases transmitted through sexual intercourse.
In addition, a contact mode of transmission can be distinguished. With it, infection occurs when it is in direct contact with a source of pathogens and introduced onto the surface of the mucous membranes and skin (for example, with scabies)
An example of a disease with a blood contact transmission mechanism
The urgent medical and social problem is that many people do not know or ignore the methods of transmission of sexual infections, are not protected during casual relationships. That is why STDs are often diagnosed by doctors.
An example of an infection with a blood contact transmission mechanism is HIV. With this disease, the immune system is affected. It gradually collapses to the formation of AIDS (acquired immunodeficiency syndrome). The causative agent is a virus from the family of retroviruses. The source of infection is a sick person.
Sexual and vertical methods 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 treatment and diagnostic procedures, drug administration, and performing tattoos in non-sterile conditions.
Nosocomial infections
Nosocomial infections ( nosocomial infections) deserve special attention . This is a very serious problem. With nosocomial infections, people become infected when they arrive at the hospital or seek medical help. Nosocomial infections cause significant damage to health. In addition, they increase the duration of treatment and the time spent in the medical institution, cause complications, and sometimes even lead to death.
Methods of transmission of infection in a medical institution are diverse. Pathogens enter human organisms both by natural (fecal-oral, aerosol-aerogenic) and artificial (during invasive medical and diagnostic procedures) routes. Nosocomial infections arise not only due to non-compliance with the sanitary-hygienic and anti-epidemic regime, but also due to the appearance of microorganisms that are resistant to chemotherapy, antibiotics, and adverse environmental factors.
In conclusion, it is worth noting that for each disease there are specific ways (methods) of transmission of infections. Knowing how infection occurs, you can prevent the occurrence of some ailments in yourself (for example, do not use dirty foods, avoid random sexual intercourse, lead a healthy lifestyle and refuse drugs).