A Infectious or etiological agent Is a living organism or molecule that causes an infectious disease (National Academy of Medicine of Colombia, 2017). If the microorganism causes disease in humans it is called a pathogen.
Another definition of infectious agent are microorganisms, helminths and arthropods that are capable of producing infection and infectious disease (Mata, 2017).
Flu virus
On the other hand, infection is called the infectious agent that penetrates the recipient organism and consequently is implanted or multiplied within it (Mata, 2017).
Another way to assimilate the term"infection"is to understand it as the successful colonization of the host by the microorganism (Lumen, 2017).
Disease is understood to be any condition in which the normal structure or functions of the body are damaged or deteriorated (Lumen, 2017).
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 effects on the health of diseases in specific populations is called Epidemiology .
Characteristics of the infectious agent
1- Physical characteristics
Size
The infectious agent may be invisible to microscopic dimensions of thousandths or millionths of a millimeter or visible, such as a tapeworm (which can reach meters in length).
Shape
Some microorganisms are endowed with a well-defined form such as viruses and others, such as bacteria, is difficult to recognize among several species.
2- Chemical characteristics
They are the chemical substances, genetic material or protein 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 monads are fully equipped for reproduction.
3- Biological characteristics
They are the attributes of the agent related to its metabolism and vital functions (Mata, 2017).
Epidemiological chain
The Ecological Triad Is the classic representation that illustrates the interaction of Guest , of the Etiological agent And the environment To understand the triggering of diseases.
He Infectious agent Is the one that bursts into or into the body of a living organism.
He environment Refers to the physical, biological, and geographic external elements that affect them and the agents.
He Guest Is the organism that receives the infectious agent.
Groups of infectious agents or pathogenic microorganisms
1- Bacteria
They are the prokaryotes, a diverse group of microorganisms formed by a single cell in which there is no nuclear membrane and has a simple wall (Oxford-Complutense Dictionaries, 2004, page 63).
Bacteria are the cause of diseases such as tuberculosis, typhoid and cholera.
2- Virus
It is a genetic agent that has no metabolism or cellular organization (Pan American Health Organization, 2017).
Yellow fever, influenza, rabies, poliomyelitis, and smallpox are virus-borne diseases.
3- Fungi
They are heterotrophic eukaryotic organisms (cells with nucleus) that need other living beings to feed themselves. They use the cell wall to absorb nutrients.
Thanks to them there is histoplasmosis and moniliasis.
4- Helminths
They are a group of parasites that are lodged in the human body. They are divided into two groups: roundworms (Nematyhelmintes) and flatworms (Platyhelmintes).
They are the cause of uncinariasis, trichinosis and cysticercosis
5- Protozoa
Eukaryotic unicellular organisms with a well-defined nucleus (UCLA School of Public Health, 2017). They live in humid environments and water.
Protozoa are responsible for diseases such as amebiasis and Chagas disease.
6- Chlamydias
They are bacteria belonging to the family Chlamydiaceae, order Chlamydiales, filo Chlamydiae. These prokaryotes have the particularity that only affect humans.
These are the agents responsible for psittacosis and trachoma.
7- Rickettsia
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 that they produce are: Typhoid, trench fever, anaplasmosis, ehrlichiosis (erliquiosis) and trench fever.
8- Spirochetes
They are another type of granmegativas bacteria that do not have polar scourges but endoflagelos.
Syphilis is produced by a type of spirochete.
Characteristics of the infectious agent when interacting with the host
They are the effects that an infectious agent is capable of producing from the moment it comes into contact with its host host.
1- Pathogenicity or pathogenic power
It is the ability of a bacterium to cause infection (Ruiz Martín & Prieto Prieto, 2017). The pathogenic power does not necessarily lead to the development of the disease because it also depends on the characteristics of the receptor of the etiological agent.
In epidemiology, this factor is measured by the mortality rate , Which results from dividing the number of patients of a certain disease by the population exposed to this disease.
2- Virtulence
It is the ability of the infectious agent to produce severe illness or death. Virulence is conditioned by the microorganism's invasiveness and its toxigenicity (Ruiz Martín & Prieto Prieto, 2017).
The virulence index is the Fatality rate , Which results from dividing the number of deaths of a certain disease by the number of patients of the same.
3- Ineffectiveness or Transmissibility
It is the capacity to infect the host, that is, to penetrate, reproduce and implant in it (Mata, 2017).
To measure this aspect, the prevalence, seroprevalence, incidence and rate of attack are used as indicators.
4- Antigenicity
It is the ability to induce the host to an immune response. The foregoing means that, upon detection of the pathogen in the host, antibodies are formed which attempt to eliminate the agent.
Communicable Diseases
Disease caused by a specific infectious agent (Pan American Health Organization, 2017) or by its toxic products. Transmission may be direct or indirect.
They can be of two types:
Emerging diseases
It is the type of communicable disease that reports an increase in humans the last 25 years.
Reemerging diseases
It is a communicable disease known in the past that after its considerable diminution, reappears.
References
- National Academy of Medicine of Colombia. (2017, 78). 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, 78). Retrieved from Universitat Oberta: cv.uoc.edu.
- Lumen. (2017, 78). Characteristics of INfectious Disease . Retrieved from Lumen: courses.lumenlearning.com.
- Mata, L. (2017, 78). The infectious agent. Recovered from BINASSS: National Library of Health and Social Security: binasss.sa.cr.
- Ruiz Martín, G., & Prieto Prieto, J. (2017, 78). General aspects of infectious agent and host . Recovered from Complutense Scientific Journals: magazines.ucm.es.
- UCLA School of Public Health. (2017, 78). Microbiological Classification of. Retrieved from UCLA Fielding School of Public Health: ph.ucla.edu.