Epidemic and Pandemic Diseases

Introduction

Many of us may have heard the word epidemic disease before. Before knowing about epidemic diseases, let's know the real definition of an epidemic. In this tutorial, we will be discussing epidemic and pandemic diseases.

What are Epidemic Diseases?

An epidemic disease is a condition in which a disease is widespread for a temporary period of time in a specific geographic area. Epidemic diseases are infectious and can spread very quickly.

It spreads to a greater extent when the sources of infection and those likely to be infected are abundant. Factors that can be responsible for an epidemic −

• As a result of a new increase in the level of the infecting virus or the disease it causes

• Evidence of recent infection has been found in areas where it was not previously present

• Improved means of transmission or disease transmission have resulted in more susceptible individuals being exposed to the disease.

• Alteration of the response of susceptible individuals to the source of infection

• The sensitive person's exposure increases through the introduction of new entrances.

Types of Epidemic Diseases

There are three main types of epidemic diseases namely,

• Point source outbreak

• Constant Source

• Person to Person.

The first two come under common sources and the third one is a person-to-person transmission which is come under Propagated source.

What is a Common Source?

An epidemic is considered to be caused by a common source when an infectious agent or toxin from the same source affects a group of people. Now we will learn about the three main types of sources of epidemics.

• Point source outbreak − It is a type of epidemic in which in all cases people are infected by a specific source at the same time. Example − Case of leukaemia after the atomic bomb explosion in Hiroshima.

• Constant source − An epidemic in which a casual infectious agent or vector of infection continues to infect people for a long period of time through known regular sources, such as contaminated water and food.

• Person-to-Person source or Propagated Source − A type of epidemic in which the causative agents or vectors of infection are spread from one person to another, thereby allowing the epidemic to spread. Effects resulting from this source usually diminish after a few generations.

• mixed type of epidemic − There is also another type called a mixed type of epidemic which has considerable similarities with common sources as well as propagated sources. For example, Shigella bacteria causes an infection called shigellosis, 3000 women were infected and each of them attended a national music festival and many of them returned home with symptoms.

Symptoms included diarrhoea (sometimes bloody), fever and abdominal pain. And the common source of all of them was that musical program.

There are even some epidemics that do not fall under common-source or propagated sources—for example, Lyme disease. Lyme disease is caused by the bacteria Borrelia burgdorferi and, rarely, Borrelia mayoni.

It is spread to humans through the bite of an infected black-legged insect (ticks). Its common symptoms include fever, headache, fatigue, and a characteristic skin rash called erythema migrans.

Other examples of epidemic diseases include −

• The Third Cholera (1852-1860)

• The Asian Flu (1957)

• SARS (2003)

• Ebola (2014).

What are Pandemic Diseases?

This type of diseases spread over a large area such as several continents or the entire world. It infects and kills more people than an epidemic. Pandemic is a new source of infection that has never caused disease before.

• Travel, antibiotic resistance and mobility increase the risk of pandemics in humans. The World Health Organization has declared the recent outbreak of COVID 19 as a global pandemic. There have been 3 waves of COVID 19 in India so far.

• HIV/AIDS is another one of the deadliest pandemics that has spread throughout the world. The disease is easily spread through sexual intercourse with an infected person, needles used by an infected person, blood etc.

• Another example of a pandemic is influenza which has occurred more than once. Now, however, it is no longer at a pandemic level. But its strains keep changing and are different from all existing viruses. This is caused by changes in the HA and NA proteins.

The number of people killed in a pandemic is determined based on -

• How severe is the illness created by the particular virus?

• How many people are affected by it?

• The degree to which people are at risk such as what age group is most at risk

• How effective are efforts to prevent it?

There are some lists of pandemics namely,

• Covid-19

• HIV/AIDS

• Spanish Flu.

There are six levels of pandemic alert declared by the World Health Organisation. That means low risk to high risk.

• Level 1 − Viruses originating from certain animals have not infected humans.

• Level 2 − Viruses originating from animals have spread to humans

• Level 3 − At this stage, the disease is limited to a limited number. This means if the illness spreads from person to person, it is not wide enough for a community-wide outbreak.

• Level 4 − If there is a community outbreak, the disease begins to spread through infected individuals.

• Level 5 − The disease has already engulfed people in several countries

• Level 6 − In at least one other completely different country, the disease has spread at the community level

There is a saying that prevention is better than cure. Though, this saying may not be very effective in preventing the spread of the virus. Even science may take some time to discover a vaccine against a particular virus. Even if a vaccine is discovered, those most likely to get sick after it is discovered, i.e. those whose immune system is too weak to fight the virus, will be the first in line to receive the vaccine.

Conclusion

An epidemic is the spread of infectious and contagious diseases in a geographical area such as a country, while a pandemic is the spread of the same disease to multiple geographies or continents.

FAQs

Q.1 What is an epidemic?

Epidemic is a disease that causes widespread infection in a population within a specific location.

Q.2 What is Pandemic?

Pandemic is the more violent form of an epidemic that transcends geographical boundaries and spreads across multiple continents.

Q.3 What are some examples of Epidemic diseases?

Cholera, Dengue, Chikungunya, Malaria, Ebola etc can be considered epidemic diseases.

Q.4 What are some examples of Pandemic diseases?

COVID-19, HIV/AIDS, Spanish Flu, and Plague are some examples of Pandemic diseases.