Infectious Diseases

Types of Infection

A disease is a condition that, through hampering body processes, impacts only a portion of or the whole body. Infectious or non-infectious diseases, both, can cause illness. In general, non-infectious causes may be internal factors, genetic irregularities, and lifestyle, while infectious diseases are caused by pathogenic microorganisms, which are the agents causing the infection.


What Is An Infectious Disease?

Infectious diseases are the diseases of microbial pathogens, namely viruses, bacteria, fungi, and parasites. These may be transmittable or non-communicable. They may be spread by plants, humans, or insects. The agents who spread the pathogens or pass them on are called vectors or intermediaries of the disease. 


Causes of Infectious Diseases

Infectious diseases are caused by pathogens invading the body. For, e.g., a particular virus can trigger a viral infection. There are infectious agents all around us, and they come in varying forms and sizes. They may be classified on the basis of certain common features. Some of these are single-celled animals like fungi, bacteria, and viruses. Other multicellular organisms like worms are also known to cause illnesses.



Pathogens are basically the disease-causing agents. These include viroid's, nematodes, prions, arthropods, notably mites and fleas and macro-parasites such as helminths and roundworms. Such diseases arise when an organism invades the cells and tissues of the human body with an infection-causing agent that triggers the reaction of the host tissues to these pathogens, both because of the effects of the pathogen and the toxins it releases.


Types of Infectious Diseases

Infectious diseases can be classified on the basis of the causative pathogen. The main types are enlisted and described below.

  • Viral Infection

Viruses are the primary cause of viral infections like the common cold, influenza, and so on. 

The virus can enter a host's body and attaches itself to the cell where its genetic material activates, and it begins to replicate itself. The cell replicates, and the virus grows. The infection of cells then releases more viruses that can go on to infect new cells.

Few viruses alter cell structure rather than destroy the cells. For example, human papillomavirus, the Epstein Barr virus, causes uncontrollable cell replication leading to cancer.

  • Bacterial Infection

Bacteria can live in extreme environments from extreme heat to extreme cold, and even radioactive waste in any environment. Innumerable bacterial strains are present on Earth, some of which cause disease. 

Bad bacteria cause infection, and good bacteria kill bad bacteria and avoid disease. Some of the bacterial diseases that are infectious are cholera, tuberculosis, diphtheria, typhoid. These diseases are usually treated with the help of antibiotics. 

  • Fungal Infection

A fungus breaks down (using an enzyme) and consumes organic material. Fungi grow and cause infections when good bacteria are destroyed. In the upper layers of the skin, many fungal infections appear, although some penetrate into the deeper layers. When inhaled, fungal spores can cause fungal infections involving the internal layers of the body.

  • Prion Infection

A prion has no genetic material and is a protein. In case the prion is abnormally folded, it impacts the brain system, which triggers dangerous diseases such as Creutzfeldt-Jakob Illness. Such diseases spread very quickly and are particularly deadly. They do not replicate in the host but stimulate anomalous behavior in the cells of the body.

  • Other Infections

Also capable of causing communicable diseases are protozoa, helminths, and ectoparasites. 

  • Protozoa are transferred via faeces contact. Protozoan causes amoebic dysentery. 

  • Helminths encompassing flatworms and roundworms also cause human infections. 

  • Ectoparasites, including mites, lice, ticks, etc. stick themselves to the skin and induce infections.

Infectious Diseases Examples

Infectious Diseases


Common cold, influenza, AIDS, dengue fever


Typhoid, cholera, fever



Leishmania (Protozoa)


Staphylococci (Bacteria)

Sleeping sickness

Trypanosoma (Protozoa)




Modes Of Transmission

Infectious diseases are transmitted through the following means, such as: 

  • Air: Whenever an infected person sneezes or coughs, the droplets actually contain disease-causing pathogens. For example, chickenpox and measles may spread in the air and may infect others nearby.   

  • Bodily Fluids: Pass the pathogens to a safe individual by contacting an infectious individual or their bodily fluids such as spit, vomit, sweat, urine, etc.

  • Surface Transmission: Touching an infected individual's previously contacted objects or areas can cause the pathogen to transfer the infection to an unaffected person and cause illness.

  • Sexual Transmission: Diseases like Syphilis and AIDS are sexually transmitted diseases. 

FAQ (Frequently Asked Questions)

1. How Do You Reduce The Chances of Contracting An Infection?

You can prevent yourself from catching any infection by following some simple measures listed below.

  • Taking all vaccinations as they are one of the most successful forms of disease-prevention. 

  • Ensure constant sanitation for the hands.   

  • Do not fly or go to work when you are sick to prevent others from contracting the disease.  

  • Hygiene must be preserved in both the bathroom and the toilet area. 

  • Avoid exchanging personal stuff like shampoo, glass drink, toothbrush, comb, etc.

  • Keep your kitchen clean by cleaning all the utensils used and cleaning the slab before and after cooking each meal. 

  • Whilst visiting patients in hospitals, wearing a mask, gown, and using sanitizing lotions to prevent infection wherever possible is recommended.

2. What Are The Most Common Infectious Disease Symptoms?

  • The effects of infectious diseases depend on the location and form of the body-affected pathogen. 

  • Viruses are engineered to invade different cells. The rabies virus, for instance, affects the nervous system. Some viruses can cause warts, muscle aches, runny noses, etc. 

  • An individual infected by bacterial infection may encounter symptoms such as fever, swelling, fire, discomfort, inflammation, also in the lymph glands, etc.

  • Skin rashes are a hint of fungal infections. 

  • Prion disorders affect the brain and show up in a lack of memories and problems incomprehension.