To understand pandemics, the one that puts matters in context is the Spanish flu of 1918. It was caused by the H1N1 virus which had an avian origin.
A pandemic is obviously a global outbreak. It is due to a virus that is “easily and spread from person to person in an efficient and sustained way,” according to The Center for Disease Control. How easily spread? During the Spanish flu, nearly one-third of the world population between 1918 and 1919 was infected by H1N1. (An epidemic, by contrast is not global, but also spreads fast. The 2013 Ebola epidemic in Western Africa which killed about 11,000 people.)
The panic caused by a pandemic is the result of a lack of information, leadership, and a slow response. In the 2009 pandemic (the H1N1 ‘flu), it took 26 weeks for a vaccine to become available. Not too long ago, Bill Gates warned about our need for preparedness for a pandemic. As we get to grips with the gravity of COVID-19 and pandemic we are living in, it’s worth watching his TED Talk on this.