By Bernard Choi, PhD

Senior Research Scientist

Public Health Agency of Canada

Ottawa, Canada

(AMNET founder member since 2003)

Background: On March 11, 2020 COVID-19 was declared a pandemic by the World Health Organisation (WHO). What is a pandemic? How is it different from an epidemic? What are some past pandemics and epidemics?

The Fact:

A pandemic is a worldwide spread of a new infectious disease. The word is from the Greek "pan" meaning "all" and "demos" meaning "people". The term refers to the spread of disease, not its potency or deadliness. The WHO define a pandemic as "an outbreak of a new pathogen that spreads easily from person to person across the globe". In history there have been a number of devastating pandemics, including the black death and smallpox. The black death way back in 1347 killed 50% of Europe’s population. In 1980, WHO officially declared eradication of smallpox by vaccination. The most recent pandemic is the 2009 swine flu caused by H1N1. It killed 200,000 people worldwide. There are two current pandemics in the world – COVID-19 and HIV/AIDS (Human immunodeficiency infection/ acquired immune deficiency syndrome).

Some examples of pandemics:

An epidemic is a spread of a disease among a large number of people in a given population. The word is from the Greek 'epi' meaning 'upon' and 'demos' meaning 'people'. While a pandemic is global, an epidemic is more local. In 1854, John Snow mapped cholera deaths in London, and identified contaminated water from the Broad Street pump as the source of the epidemic. There have been 21 epidemics since 2010, including the Ebola epidemic. Deaths from epidemics are usually fewer compared to pandemics. The severe acute respiratory syndrome (SARS) and Middle East respiratory syndrome (MERS) epidemics, also caused by a coronavirus (similar to COVID-19), each killed about 800 people.

Some examples of epidemics:

Look at Visualizing the History of Pandemics below (LePan, 2020). The chart (based on March 20, 2020 data) shows 11,400 COVID-19 deaths worldwide. After 4 weeks, today’s chart (April 16 data) shows 139,500 COVID-19 deaths. Global efforts, on a scale unprecedented in history, are underway to curb the COVID-19 pandemic.

Source of infographic: Nicholas LePan (2020)


1. Nicholas LePan (2020). Visualizing the History of Pandemics (First published 2020-03-14, on-going updates)

2. What is a pandemic and how is it different to an epidemic and an endemic? (2020-03-12);

3. Wikipedia. Pandemic;

4. Wikipedia. List of epidemics.;

Disclaimer: Views in this article are those of the author, and do not necessarily represent the official views of any organizations or governments.

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