Epidemic Vs Endemic Vs Pandemic: What Is The Difference?


The terms, epidemic, endemic and pandemic may sound extremely confusing in case you are hearing them for the first time. These terms are generally used to describe the level of spread of a certain disease or infection. While the terms may suggest that there is a specific threshold by which a disease or infection is declared an outbreak, epidemic, endemic or pandemic, the distinction is often not clear , even among epidemiologists. Here is the description of WHO and CDC in as far as understanding the meaning of these three terms is concern.

What Is An Epidemic?

Epidemic is a general term that is used to describe any bad situation that has grown out of control. Well, according to Centers for Disease Control And Prevention (CDC) and World Health Organization (WHO), an epidemic is an outbreak of a disease that occurs over a wide geographical area and affects an exceptionally high proportion of the population.

Sometimes, an epidemic stays contained to a certain geographical area, however, when it spreads into other countries, regions or continents, it turns into a full-blown pandemic.

Known examples of Epidemic:

  • Annual influenza epidemic follows a winter seasonal pattern in the United States with typical activity peaking during late December to early February.
  • Outbreak of Zika Virus in Brazil and United States in 2016.
  • Outbreaks of Chikungunya and dengue fever in India.
  • Ebola in west Africa and DRC Congo.

What Is An Endemic?

An endemic according to WHO and CDC, is a term that describes a constant presence or prevalence of a disease or infection within a certain geographical area. For instance, in the tropical parts of the world, mosquito-borne infection malaria can be described as an endemic.

Known examples of endemic:

  • Polio remains endemic in three countries- Afghanistan, Nigeria and Pakistan
  • Pertussis is endemic worldwide, even in areas with high vaccination rates.
  • Chickenpox is considered in the UK, but malaria is not.

What Is A Pandemic?

A pandemic according to WHO and CDC, is a term that describes an outbreak of a disease that has spread across many countries and affects a large number of people. That was the case in 2009 when WHO declared the swine flu caused by the (H1N1 flu virus) a ‘’Public Health Emergency of International Concern’’ in other words a pandemic.

In this regard, neither CDC nor WHO specifies how many countries or how many people need to be affected in order for something to be declared a pandemic. When an epidemic crosses over into a pandemic, the biggest difference is that more governments are involved in attempting to prevent further progression of the disease.

Known pandemic in history:

  • 2020 Corona virus (COVID-19) which has so far killed over 5000 people around the world.
  • The HIV/AID, which has killed over 39 million people since 1982.
  • The ongoing tuberculosis pandemic which continues to kill over 900000 people annually.
  • The Black Death was one of the worst pandemics in human history, killing at least 75 million people on three continents.
  • The Franco-Prussian War triggered a smallpox pandemic of 1870-1985 that claimed 500000 lives.
  • The 1918 Spanish influenza pandemic which is killed an estimated 50 million people.
  • The smallpox pandemic of the 20th century claimed between 300 to 500 million lives.