Infection and its various types

July 8, 2018

Introduction to infection

An infection is the detrimental colonization of a host organism by a foreign species.
In an infection, the infecting organism seeks to utilize the host’s resources to multiply, usually at the expense of the host.
The infecting organism, or pathogen, interferes with the normal functioning of the host and can lead to chronic wounds, gangrene, loss of an infected limb, and even death.
The host’s response to infection is inflammation.
A pathogen is usually considered a microscopic organism though the definition is broader, including parasites, fungi, viruses, prions, and viroids.
A symbiosis between parasite and host, whereby the relationship is beneficial to the former but detrimental to the latter, is characterized by
The branch of medicine that focuses on infections and pathogens is infectious disease.
There are various types of infections. Some of them are as follows:

Types of Infection

Infection that causes no clinically apparent symptoms is in-apparent infection.
The disease agent may multiply within the host but does not show signs and symptoms.
Sub-clinical infections can be detected only by laboratory tests.
e.g., in some diseases like rubella, mumps, polio, hepatitis A and B, a great deal of sub-clinical infection occurs.

In latent infection, the host does not shed the infectious agent which lies dormant within the host without symptoms.
Latent infection occurs in herpes simplex infection.

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Acute infections are those that come on rapidly, are accompanied by severe symptoms, and progress to climax.
An example of acute infection is measles and streptococcal pharyngitis.
These types of infections also heal rapidly.

Chronic infections occur slowly, generally are accompanied by mild to severe symptoms.
They persist over a long period of time, with an extended convalescence. E.g., tuberculosis, etc.

A localized infection remains at a specific body site, usually the first site of infection.
e.g., UTI caused by Escherichia coli.

It is the one that spread to alternative sites in the body such as deeper organs or tissues.
e.g., enteric fever caused by Salmonella typhi.

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It is established in a previously healthy body.
It is an initial localized infection that decreases host resistance and provides the way for further invasion by the same microorganisms or other microorganisms.
e.g., viral influenza.

It develops in the body after it has already been infected by different microorganisms.
It occurs after primary infection because the host resistance power is diminished by the primary infection.
e.g., Pneumococcal pneumonia following viral influenza.

References:

i) https://www.medicalnewstoday.com/articles/196271#types

I am Shailesh Koirala