A pandemic (from Greek πᾶν pan 'all' and δῆμος demos 'people') is an epidemic of infectious disease that has spread through human populations across a large region; for instance multiple continents, or even worldwide.
Whilst the subject has been explored in numerous movies and TV shows the reality is that there are so many people crowded into the world's cities and we can travel so easily between countries and continents that it wouldn't take much to start a pandemic and there have been a number of them throughout history including the Black Death (Bubonic Plague) in medieval Europe, Spanish Flu in 1918 and COVID-19 in 2020/21
Whilst none of these has caused an extinction level event there is no doubt that a global pandemic of an air borne disease that had a very high mortality rate could come very close.
To be clear, this is an extinction level event that would only impact humanity though it would have a knock-on effect on those animals that either depend upon us or feed upon us.
Here is an article from CNN that goes into some depth on this subject and presents some worrying scenarios...
and another from the Harvard Business School...
and from The Guardian newspaper...
This article contains a list of the worst pandemics along with a good collection of sources and other papers...
There are some scenarios that are a lot more plausible and likely - a global pandemic isn't an 'if' scenario, it's a 'when'.
