- Characteristics of the infectious agent
- - Physical characteristics
- Size
- Shape
- - Chemical characteristics
- - Biological characteristics
- Epidemiological chain
- Groups of infectious agents or pathogenic microorganisms
- - Bacteria
- - Virus
- - Mushrooms
- - Helminths
- - Protozoa
- - Chlamydias
- - Rickettsiae
- - Spirochetes
- Characteristics of the infectious agent when interacting with the host
- - Pathogenicity or pathogenicity
- - Virtulence
- - Ineffectiveness or transmissibility
- -
- Communicable diseases
- Emerging diseases
- Re-emerging diseases
- References
An infectious or etiologic agent is a living organism or molecule that causes an infectious disease. If the microorganism causes disease in humans, it is called a pathogen. Another definition of infectious agent is microorganisms, helminths and arthropods that are capable of producing infection and infectious disease.
On the other hand, infection is called the infectious agent that penetrates the recipient organism and consequently implants or multiplies within it. Another way of assimilating the term "infection" is to understand it as the successful colonization of the host by the microorganism.
Flu virus
Disease is understood to be any condition in which the normal structure or functions of the body are damaged or impaired.
The infectious agent is a necessary but not unique element for the disease to occur. For the development of an infection or disease, the other two constituent elements of the epidemiological triad must be intercepted: the host and the environment.
The branch of biology and medicine that studies and analyzes the patterns, causes, and health effects of diseases in specific populations is called epidemiology.
Characteristics of the infectious agent
- Physical characteristics
Size
The infectious agent can be invisible, having microscopic dimensions of thousandths or millionths of a millimeter, or visible, like a tapeworm (which can reach meters in length).
Shape
Some microorganisms are endowed with a well-defined shape like viruses and others, like bacteria, are difficult to recognize among various species.
- Chemical characteristics
They are the chemical substances, genetic or protein material that constitute the microorganism.
In the case of viruses, they lack metabolism and cellular organization that forces them to stay in a host to reproduce; while bacteria or moners are fully equipped for reproduction.
- Biological characteristics
They are the attributes of the agent related to its metabolism and vital functions.
Epidemiological chain
The ecological triad is the classical representation that illustrates the interaction of the host, the etiological agent and the environment to understand the triggering of diseases.
The infectious agent is the one that breaks into or into the body of a living organism.
The environment refers to the external physical, biological, geographical elements that affect themselves and the agents.
The host is the recipient organism of the infectious agent.
Groups of infectious agents or pathogenic microorganisms
- Bacteria
They are prokaryotes, a diverse group of microorganisms made up of a single cell in which there is no nuclear membrane and which has a single wall.
Bacteria are the cause of diseases such as tuberculosis, typhoid and cholera.
- Virus
It is a genetic agent that does not have metabolism or cellular organization.
Yellow fever, influenza, rabies, polio, and smallpox are diseases caused by viruses.
- Mushrooms
They are heterotrophic eukaryotic organisms (cells with nuclei) that need other living beings to feed themselves. They use the cell wall to absorb nutrients.
Thanks to them there is histoplasmosis and moniliasis.
- Helminths
They are a group of parasites that live in the human body. They are divided into two groups: roundworms (Nematyhelmintes) and flatworms (Platyhelmintes).
They are the cause of hookworm, trichinosis and cysticercosis
- Protozoa
Eukaryotic unicellular organisms with a well-defined nucleus. They live in humid environments and waters.
Protozars are responsible for diseases such as amoebiasis and Chagas disease.
- Chlamydias
They are bacteria that belong to the Chlamydiaceae family, Chlamydiales order, Chlamydiae phylum. These prokaryotes have the peculiarity that they only affect humans.
These are the agents responsible for psittacosis and trachoma.
- Rickettsiae
They are another type of bacteria less common than the others, which can only live in another organism. It belongs to the Rickettsiaceae family.
Some of the diseases they cause are: Typhus, trench fever, anaplasmosis, ehrlichiosis (ehrlichiosis) and trench fever.
- Spirochetes
They are another type of granmegative bacteria that do not have polar flagella but endooflagella.
Syphilis is caused by a type of spirochete.
Characteristics of the infectious agent when interacting with the host
These are the effects that an infectious agent is capable of producing from the moment it comes into contact with its recipient host.
- Pathogenicity or pathogenicity
It is the ability of a bacteria to cause infection. The pathogenic power does not necessarily lead to the development of the disease as it also depends on the characteristics of the receptor of the etiological agent.
In epidemiology, this factor is measured through the mortality rate, which results from dividing the number of patients with a certain disease by the population exposed to this disease.
- Virtulence
It is the capacity of the infectious agent to cause severe illness or death. Virulence is conditioned by the invasiveness of the microorganism and its toxigenicity.
The virulence index is the fatality rate, which is the result of dividing the number of deaths from a certain disease by the number of patients from it.
- Ineffectiveness or transmissibility
It is the ability to infect the host, that is, to penetrate, reproduce and implant in it.
To measure this aspect, prevalence, seroprevalence, incidence and attack rate are used as indicators.
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It is the ability to induce the host to an immune response. This means that, when the pathogen is detected in the host, antibodies are formed that attempt to eliminate the agent.
Communicable diseases
Disease caused by a specific infectious agent or its toxic products. Transmission can be direct or indirect.
They can be of two types:
Emerging diseases
It is the type of communicable disease that has reported an increase in humans in the last 25 years.
Re-emerging diseases
It is a communicable disease known in the past that, after its considerable decrease, reappears.
References
- National Academy of Medicine of Colombia. (2017, 7 8). Academic Dictionary of Medicine. Recovered from infectious agent: dic.idiomamedico.net.
- Oxford-Complutense dictionaries. (2004). Dictionary of Biology. Madrid: Editorial Complutense.
- The natural history of diseases. (2017, 7 8). Retrieved from Universitat Oberta: cv.uoc.edu.
- Lumen. (2017, 7 8). Characteristics of INfectious Disease. Retrieved from Lumen: courses.lumenlearning.com.
- Mata, L. (2017, 7 8). The infectious agent. Recovered from BINASSS: National Library of Health and Social Security: binasss.sa.cr.
- Ruíz Martín, G., & Prieto Prieto, J. (2017, 7 8). General aspects of the infectious agent and the host. Recovered from Complutense Scientific Journals: magazines.ucm.es.
- UCLA School of Public Health. (2017, 7 8). Microbiological Classification of. Retrieved from UCLA Fielding School of Public Health: ph.ucla.edu.