Source of infection: definition, species, identification

In our language, there are more than 600 species of known microorganisms, but we have more chances to catch infection in public transport. What is the source of the infectious disease? How does the mechanism of infection work?

Pathogenicity of organisms

Infection with pathogens is called infection. The term appeared in 1546 thanks to Girolamo Fracastoro. At present, about 1,400 microorganisms are known to science, they surround us everywhere, however, infections do not develop in us every second.

Why? The fact is that all microorganisms are divided into pathogenic, opportunistic and non-pathogenic. The former are often parasites, and require the presence of a "master" for their development. They can affect even a healthy and resistant organism.

Conditionally pathogenic microorganisms (E. coli, Candida fungus) do not cause any healthy reactions in a healthy person. They can live in the environment, be a part of the microflora of our body. But under certain conditions, for example with weak immunity, they become pathogenic, that is harmful.

The term "non-pathogenic" implies the absence of danger in the interaction with these organisms, although they can penetrate the human body and cause the development of infection. The boundaries between the conditionally pathogenic and non-pathogenic microflora in microbiology are very fuzzy.

Source of infections

Infectious disease can be caused by the penetration into the body of pathogenic fungi, viruses, protozoa, bacteria, prions. The source of infectious agents is the environment that promotes their development. This environment is often a man or an animal.

Getting into favorable conditions, microorganisms actively multiply, and then leave the source, finding themselves in the external environment. There, pathogenic microorganisms, as a rule, do not reproduce. Their number gradually decreases until complete disappearance, and various unfavorable factors only accelerate this process.

To resume vital activity in microorganisms is obtained when they find a new "master" - a vulnerable person or animal, whose immunity is weakened. The cycle can be repeated continuously, while the infected will spread the parasites to healthy organisms.

Environment as a transmitter

It is important to understand that the environment is not the source of infection. It always acts as an intermediary for the transfer of microorganisms. Insufficient moisture, lack of nutrients and inadequate temperature of the environment are unfavorable conditions for their development.

Air, everyday objects, water, soil first themselves are exposed to infection, and only then they transport the parasites to the host's body. If microorganisms are in these environments for too long, they die. Although some are particularly resistant and can persist even in adverse conditions for many years.

Anthrax has a strong resistance . In the soil, it persists for several decades, and when boiled, it dies only an hour later. He is also completely indifferent to disinfectants. The causative agent of cholera El Tor is able to remain in soil, sand, products and feces, and warming the reservoir to 17 degrees allows the sticks to reproduce.

Sources of infection: species

Infections are divided into several types, according to what organisms they multiply and to whom can be transmitted. Based on these data, anthroponoses, zooanthrotonoses and zoonoses are isolated.

Zooanthronoses or anthropozoonoses cause diseases in which the source of infection is a person or an animal. In humans, infection most often occurs through animals, especially through rodents. Zoonotic infections include rabies, sap, tuberculosis, leptospirosis, anthrax, brucellosis, and trypanosomiasis.

Anthroponotic disease is when the source of infection is a person, and it can only be transmitted to other people. This includes recurrent, typhus and typhoid fever, chickenpox, gonorrhea, influenza, syphilis, whooping cough, cholera, measles and poliomyelitis.

Zoonoses are infectious diseases, for which the animal's organism is a favorable environment. Under certain conditions, the disease can be transmitted to people, but from person to person - not. The exception is the plague and yellow fever that can circulate among people.

Detection of infection

An infected person or animal can cause widespread disease within one, several localities, and sometimes several countries. Dangerous diseases and their spread are studied by epidemiologists.

If there is at least one case of infection, doctors find out all the details of the infection. There is a detection of the source of infection, determining its type and ways of spreading. To do this, most often used epidemiological anamnesis, which consists in questioning the patient about recent actions, contacts with people and animals, the date of manifestation of symptoms.

Complete information about the infected is extremely useful. With its help it is possible to find out the route of transmission of infection, a possible source, and also the potential scale (whether the case will be single or massive).

The initial source of infection is not always easy to identify, there may be several. This is especially difficult to do with anthropozoonosis. In this case, the main task of epidemiologists is the identification of all potential sources and transmission routes.

The methods of transmission

There are several mechanisms of transmission of infection. Fecal-oral is characteristic of all intestinal diseases. Malicious microbes are in abundance in feces or vomit, in a healthy body they enter with water or contact-household way. This happens when the source of infection (a sick person) badly washes the hands after the toilet.

Respiratory, or air-droplet acts in viral infections that affect the respiratory tract. The transfer of microorganisms occurs when sneezing or coughing near uninfected objects.

Transmissible means transmission of infection through the blood. This can happen when bitten by a carrier, such as a flea, tick, malarial mosquito, lice. Pathogens that are located on the skin or mucous are transferred by contact. Penetrate into the body through wounds on the body or during a touch to the patient.

Sexually transmitted mainly venereal diseases, usually directly during sexual contact. The vertical mechanism of transmission represents infection of the fetus from the mother during pregnancy.

Specificity of transmission of infection

For each type of microorganism, its mechanism is characteristic, through which viruses or bacteria enter the host's body. As a rule, there are several such mechanisms, and certain environmental factors can sometimes contribute to the transmission of parasites.

At the same time, the way that fits one microbe does not help the transfer of others. For example, many pathogens of respiratory infections are absolutely powerless before gastric juice. Getting into the gastrointestinal tract, they die and do not cause the development of the disease.

Some mechanisms of getting harmful microbes into the body can, on the contrary, accelerate the development of the disease. So, getting the causative agent of syphilis into the bloodstream with the help of an infected medical needle causes complications. The disease proceeds more intensively.

Conclusion

Infection is a combination of biological processes that arise and develop in the body when introducing pathogenic microflora into it. An illness can strike both a person and an animal. The main mechanisms of transmission are contact, sexual, airborne, fecal-oral, vertical pathways.

The source of the infection is an environment favorable for reproduction and distribution of microbes. People and animals often have suitable conditions. The environment, as a rule, acts as an intermediary.

It usually does not have the conditions for the life of pathogenic and conditionally pathogenic microorganisms. Long stay in the environment contributes to their extinction. In some cases, microorganisms can persist in soil, water, sand from a few days to decades.