what is a pathogen? and the 4 main pathogens

The term pathogen came into use in the 1880s and was coined from Greek word “pathos” and “genēs” which means “suffering” and “producer of” respectively, which means pathogen can be said to be producer of suffer

Typically, pathogen is used to describe a disease causing microscopic agents, such as a bacterium, virus, fungus and parasite

The scientific study of microscopic organisms, including microscopic pathogenic organisms is called microbiology, while the study of disease that may include these pathogens is called pathology.

Pathogenic organisms have a single goal, which is to survive and multiply in their hosts.

Pathogens are specially adapted to infect a host, bypass the host’s immune responses, reproduce within the host, and escape its host for transmission to another host and therefore, disrupt the normal physiology of a multi-cellular animal or plant.

However, pathogens can infect unicellular organisms from all of the biological kingdoms.

There are several substrates and pathways whereby pathogens can invade a host.

The human body contains many natural defences against some of common pathogens in the form of the human immune system and by some “helpful” bacteria present in the human body’s normal flora.

Some pathogens are responsible for massive amounts of casualties and have had numerous effects on afflicted groups.

Today, many medical advances have been made to safeguard against infection by pathogens.

Social advances such as food safety, hygiene, and water treatment have reduced the threat from some pathogens.

What are the different types of Pathogens?

Pathogens vary in different ways and there are different pathogens with variable modes of infections. There are four main pathogens namely

  • Viruses
  • Bacteria
  • Fungi
  • Parasites

definition of pathogen in biology

Virus as a pathogen

A Virus is a non-living piece of genetic code, such as DNA or RNA, and protected by a coating of protein.

In the case of viral infection, viruses invade host cells within your body, and then use the components of the host cell to replicate, producing more viruses.

After the replication cycle is complete, these new viruses are released from the host cell.

Some viruses can remain dormant for a time before multiplying again. When this happens, a person appears to have recovered from the viral infection, but gets sick again.

Anti viral drugs are used for viruses while Antibiotics do not kill viruses and therefore are ineffective as a treatment for viral infections.

Bacterium as a pathogen

A Bacterium is a unicellular microorganism. It is diverse and have a variety of shapes and features, and have the ability to live in just about any environment, including in and on your body. It is essential to note that not all bacteria cause infections. The bacteria with the potential to induce infections are said to be pathogenic.

Antibiotics are used to treat bacterial infections. Some strains of bacteria have become resistant to antibiotics, making them difficult to treat. This can happen naturally, but also happens because of the overuse of antibiotics, according to the World Health Organization.

Fungus as a pathogen

A Fungus cell has a nucleus and other components protected by a membrane and a thick cell wall. Their structure can make them harder to be eradicated.

Some new strains of fungal infections are proving to be especially dangerous, such as Candida aurus, and have prompted more research into fungal infections.

helminth as  a  parasitic pathogen

Parasite as a pathogen

Parasites are organisms that behave like tiny animals, living in or on a host and feeding from or at the expense of the host.

Though parasitic infections are more common in tropical and subtropical regions, they can occur anywhere.

Three main types of parasites can cause disease in humans. These include:

  • protozoa, which are single-celled organisms that can live and multiply in your body
  • helminths, which are larger, multi-celled organisms that can live inside or outside your body and are commonly known as worms
  • ectoparasites, which are multi-celled organisms that live on or feed off your skin, including some insects, such as ticks and mosquitos “biologically known as vector while the plasmodium transmitted by mosquitoes is a protozoan”

They can spread in several ways, including through contaminated soil, water, food, and blood, as well as through sexual contact and via insect bites.

Different diseases caused by different pathogens

Viruses, bacteria, fungi and parasites cause variety of infections, which we will be looking at in this article

Virus as a pathogen and some of the infections it causes

Viruses can cause a number of infections, many of which are contagious. Examples of viral diseases include:

Bacterium as a pathogen and some of the diseases it causes

  • tuberculosis
  • cellulitis
  • cholera
  • gonorrhea

Fungus as a pathogen and some of the diseases it causes

  • ringworm
  • thrush
  • athlete’s foot

Parasite as a pathogen and some of the diseases it causes

  • malaria
  • giardiasis
  • intestinal worms

Routes of transmission of pathogens

Pathogens are transmitted either directly or indirectly.

Direct transmission involves the spread of pathogens by direct body-to-body contact.

This type of direct transmission (mother-to-child) is also known as vertical transmission.

Pathogens can also be spread by indirect transmission, which involves contact with a surface or substance that is contaminated with pathogens. It also includes contact and transmission through an animal or an insect vector.

Types of indirect transmission include:

  • Airborne 

Pathogen is expelled (typically by sneezing, coughing, laughing, etc.), remains suspended in air, and is inhaled by or comes in contact with respiratory membranes of another person

  • Droplets 

Pathogens are contained in droplets of body fluid (saliva, blood, etc.) contact another person or contaminate a surface. Saliva droplets are most commonly spread through sneezing or coughing

  • Foodborne 

Transmission occurs through eating contaminated food or by improper cleaning habits after handling contaminated food.

  • Waterborne 

Pathogen is spread by consumption or contact with contaminated water.

  • Zootonic 

Pathogen is spread from animals to humans. This includes insect vectors that transmit disease through biting or feeding and transmission from wild animals or pets to humans.

types of pathogens

While there is no way to completely prevent pathogen transmission, the best way to minimize the chances of acquiring a pathogenic disease is by maintaining good hygiene.

These include-

  • Wash your hands often both during indoors or outdoors activities
  • Get vaccinated and ensure vaccinations are up to date
  • Prepare, cook, and store meat and other food items properly
  • Avoid sharing drinking glasses or utensils
  • Protect against insect bites
  • Travel wisely by getting informed about health risks and special vaccinations
  • Practice safe sex.

pathophysiology of scabies

community common health issues


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