Infectious Diseases: Definition, Types & Preventive Measures

You have landed on the right page to learn about Infectious Diseases. Since the year 2020, the entire world is suffering from a dangerous infectious disease, COVID-19. Do you know COVID-19 falls under which category of disease? Coronavirus Disease (COVID-19) is an example of an infectious disease caused by coronaviruses.

Apart from COVID-19, there are a lot more examples of infectious diseases like Chickenpox, Malaria, Pneumonia, Measles, Mumps, etc. In this article, we are going to learn more about infectious diseases as well as how it differs from other kinds of diseases, i.e. Non-Infectious diseases. Continue reading to know more.

What are Infectious Diseases?

Infectious diseases are diseases that are transmitted from an infected person to a healthy person. Infectious diseases are also called communicable diseases or transmissible diseases. These diseases are mostly caused by microorganisms such as fungi, bacteria, viruses or parasites. Infectious diseases can be transmitted by air, water, food, vectors, etc.

Difference Between Infectious and Non-infectious Diseases

Do you think all diseases can be caused from person to person? The correct answer is ‘NO’. Not all diseases are infectious. Diseases that are not caused by direct contact with an infected person are called non-infectious diseases. In simple words, infectious diseases can be transmitted from one person to another, while non-infectious diseases cannot be transmitted from one person to another.

Let us understand the difference between infectious and non-infectious diseases in detail:

Types of Infectious Diseases

Now, we all know that infectious diseases are caused from one person to another through contaminated water, air, food items, etc. Let’s move further to learn about different types of infectious diseases. Infectious diseases can be broadly classified into two categories:
1. Classification based on Mode of Transmission
2. Classification based on Causative Organisms (Pathogens)

Classification based on Mode of Transmission

The infectious diseases transmitted from a diseased person to a healthy person based on the mode of transmission can be of two types:

1. Direct Transmission: The pathogens of disease can infect a healthy person directly without an intermediate agent. It can take place in the following ways:
a. Direct contact between an infected person and a healthy person
b. Droplet infection

Fig: Types of Direct Transmission of Infectious Disease

2. Indirect Transmission: The pathogens of certain diseases infect the human body through some intermediate agents. It can take place in the following ways:
a. Airborne: Airborne transmission happens when infectious microorganisms are carried by dust or droplet nuclei suspended in the air.
b. Vehicleborne: Different types of vehicles may passively carry pathogens. Vehicles that indirectly transmit an infectious disease involve food, water, biological products (e.g., blood), and fomites (e.g., inanimate objects like napkins, bedding, or surgical knives).
c. Vector-borne: Vectors like mosquitoes, fleas, insects, and ticks may carry pathogens through purely involuntary means or may support the growth or reproduction of the pathogen in their body. Bite or contact with these infected agents may cause the respective diseases.

Fig: Types of Indirect Transmission of Infectious Disease

Classification based on Causative Organisms (Pathogens)

Infective diseases are caused by different causative organisms or pathogens (disease-causing microorganisms). The causative agents can be viruses, bacterias, or worms.

Fig: Classification based on Causative Organisms (Pathogens)

1. Disease caused by Bacteria: Bacteria can live in all kinds of environments, from extreme heat to severe cold and even radioactive wasteland. A bacterial infection is the multiplication of harmful strains of pathogenic bacteria in the body. Pneumonia, meningitis, and food poisoning are some diseases that may be caused by pathogenic bacteria. These diseases can be treated by antibiotics, but some bacteria become antibiotic-resistant and cannot be treated.

Some of the other common bacterial diseases are mentioned below:

2. Diseases caused by Viruses: There are many types of viruses that cause a wide range of viral diseases. The most common type of viral disease is the common cold caused by a viral infection of the upper respiratory tract (nose and throat). Some of the other common viral diseases are mentioned below:

3. Disease caused by Protozoa: Protozoa are single-celled organisms classified as eukaryotes. Protozoa are found everywhere, and some of these are parasites. Infectious diseases caused by protozoa can be caused through ingestion of cysts (the dormant life stage), sexual transmission, or through insect vectors. Some of the common protozoan diseases are mentioned below:

4. Disease caused by Fungi
Fungi are saprophytes that can infect animals and plants. Many fungal infections develop on the upper surface of the skin while some penetrate into deeper layers. Inhaling fungal spores may cause fungal infections that affect the whole body. Following are some examples of infectious diseases caused by fungus:

5. Diseases caused by Helminths
Helminths are parasitic worms that cause disease in humans and other animals. It is broadly classified into tapeworms, flukes, and roundworms. These often live in the gastrointestinal tract of their hosts but may also burrow into other organs and induce physiological damage. Ectoparasites like mites, lice, ticks, etc., attach to the skin and cause infections. Below are some examples of diseases caused by helminths:

Preventive Measures of Infectious Diseases

Preventive measures are the measures or the steps taken in order to prevent disease. As we all are living in the age of science and technology, treatment for almost all diseases are available. But, there are few diseases that cannot be treated, or we can say the treatment of it is not yet discovered. Such diseases can only be controlled and prevented by taking suitable preventive measures. Following are some treatment and preventive measures that can be practised to prevent or treat respective infectious diseases:

1. Treatment depends on which microorganism causes the infection. Most bacterial diseases can be treated with antibiotics which usually kill the bacteria to end the infection.
2. Viral infections are commonly treated with supportive medications such as antiviral medications, increased fluid intake, and rest.
3. Fungal and parasitic infections are treated with antifungal medications,e.g., fluconazole and antiparasitic drugs like mebendazole, etc.
4. We can also reduce the risks of c infectious diseases by frequently washing hands with soap and water, covering the nose and mouth while sneezing or coughing.
5. Regularly sanitizing touched surfaces at home or workplace.
6. Evading contact with an infected person or sharing personal items with them.
7. Avoid drinking or swimming in contaminated water supplies.
8. Avoid eating or drinking from unhygienic sources of food and beverages.

Fig: Preventive Measures to Avoid Infectious Diseases

Summary

Infectious diseases can be transmitted from infected persons to healthy persons. The mode of transmission may differ, it can be direct transmission (direct contact and droplet infection), or it can be an indirect transmission, i.e. through an intermediate agent (by vector-borne, vehicle-borne, airborne). Infectious diseases are caused by causative organisms or pathogens like viruses, bacteria, or worms.

Symptoms of infectious diseases should be identified, and preventive measures should be taken accordingly. Vaccination is an effective preventive measure to stop or slow down the spread of infectious diseases.

Frequently Asked Questions

Q.1. What are 5 infectious diseases?
Ans: Chickenpox, COVID-19, Common cold, Influenza, Cholera are five examples of infectious diseases.

Q.2. What are the 4 types of microbes that cause infections?
Ans: The four types of microbes that cause illness in animals are bacteria, fungi, viruses, and parasites. Parasites can be endoparasites or ectoparasites.

Q.3. What are the 10 common infectious diseases?
Ans: Pneumonia, Chickenpox, HIV, Malaria, Hepatitis, Common cold, Rubella, Influenza, Tetanus, Mumps are ten common infectious diseases.

Q.4. Which infectious disease kills the most?
Ans: Tuberculosis or TB kills 1.6 million people every year or 4,000 people a day. It is an airborne disease caused by Mycobacterium tuberculosis.

Q.5. What’s the worst disease in history?
Ans: Black death or Plague is considered the worst disease in history. It was a bubonic plague pandemic caused by the bacterium Yersinia pestis. It is the fatal pandemic recorded in human history, causing the death of 75-200 million people.

We hope this detailed article on Infectious Diseases helps you in your preparation. If you get stuck do let us know in the comments section below and we will get back to you at the earliest.