Know the contagion: Endemic, Epidemic or Pandemic?

Biotechnology & Healthcare New Born Screening
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Contagious diseases spread by either bacteria or viruses and are like, always present in society. Generally, infected cases are present below an expected threshold, but from time to time there might be an outbreak, a new strain or a new sickness that has a huge impact at either a local or global level. The speed and pace of new cases, can be grouped as:

Endemic-describes a disease that exists permanently in a population

Epidemic- is an outbreak that influences numerous people at one time and can spread through one or few networks

Pandemic – is the term used to depict an epidemic when the spread is worldwide.

Let’s have a broader understanding of these disease trends.


Endemic (Greek ‘en’ meaning ‘in’ and ‘demos’ meaning ‘people’): This term is used to describe a disease that is present consistently in a society or a nation. Each country may have a disease that is unique, for instance:

Dengue is yet present because of the inability to eradicate the Aedes aegypti mosquito. However, the failure to destroy the Aedes mosquito in various region of the world led to continued transmission of the disease throughout the region and then returning back to civilization causing several epidemics.  Similarly, diseases like varicella and malaria occur in various parts of the world as endemics.


Epidemic (Greek words ‘epi’ meaning ‘upon’ or ‘above’ and ‘demos’ meaning ‘people’ and in this context, in a large number of people): The terminology Epidemic is used portray a situation where a disease spreads quickly to an enormous number of individuals in a given populace, over a short period of time.

The term epidemic is not just used for infectious diseases, it is also used for any circumstance that prompts a detrimental rise of health risks within a community. For instance:

The rise in obesity throughout the world and most especially in Western countries is an epidemic wide spreading specially in the United States.

When the term epidemic is used for an infection, or in connection with any infectious disease, it is due to the abrupt rise of cases resulting from a novel infectious agent or any kind of mutation or change in the existing agent, for example:

  • An infectious agent migrating from one host to another, for instance moving from animals to humans (zoonotic disease)
  • A genetic mutation in the infectious agent like bacteria, fungi or any parasite.
  • Introduction of a previously unknown pathogen to a host population

Epidemics usually follow a predictable pattern and these patterns are often used to screen, predict and control the widespread of the infection.


The term ‘Pandemic’ gets coined from ‘pan’ meaning all and ‘demos’ meaning people and is used to describe the rapid widespread of a contagious disease across several continents or throughout the world. In simpler terms, once an epidemic becomes global and infects a larger part of the population, it becomes a pandemic.

Enlisted below, are the features of a pandemic:

  • A pandemic affects a geographical area, often the whole world
  • Number of infections in a pandemic is very high
  • A pandemic is usually the result of a new strain of a virus/bacteria or a pathogen that has earlier been either dormant or unknown
  • Fatality rate in a pandemic is higher
  • Pandemic require tougher containment measures leading to social disruption, unrest and economic loss

When does an epidemic escalate to a pandemic?

The apex health body, the World Health Organization declares an epidemic to a pandemic only when the number of cases in an epidemic shows a dramatic exponential growth, with increase in the number of infections in a manner like each day showing many more cases than the previous day.

The existing Coronavirus Disease (COVID-19) is the perfect example of a pandemic.

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