‘Pandemic’ vs. ‘Epidemic’—What's the Difference?

Today, CNN announced it would be calling the coronavirus disease COVID-19 a pandemic even though the World Health Organization (WHO) and the U.S. Centers for Disease Control (CDC) are still sticking with “epidemic” for now.

So what’s the difference between a pandemic and an epidemic?

‘Pandemic’ Versus ‘Epidemic’

Generally speaking, a pandemic is more serious than an epidemic. A pandemic spreads wider and affects more people. 

A pandemic is an epidemic that has spread over several countries or continents, usually affecting a large number of people.

According to the CDC, an epidemic is "an increase, often sudden, in the number of cases of a disease above what is normally expected in that population in that area,” and a pandemic is “an epidemic that has spread over several countries or continents, usually affecting a large number of people.”

Those definitions are subjective, and it’s not as if there’s a scientific test that reveals that, yes, suddenly at this one specific moment, we meet the criteria for a pandemic. But since the virus has now affected more than 100,000 people worldwide, is in more than 100 countries, and is on every continent except Antarctica, COVID-19 seems to meet the general criteria for a pandemic.

In fact, in a press conference this morning, the director-general of the WHO, Tedros Adhanom Ghebreyesus, said “the threat of a pandemic has become very real," but community transmission is still limited to a smaller number of countries. The executive director of the WHO World Emergencies Program, Mike Ryan, said that if this were influenza, they would have already called it a pandemic, but he further explained their resistance to using the word by citing concern that doing so could cause more harm than good. He said, “For me, I’m not worried about the word, I’m concerned about the world’s reaction to the word. Will we use it as a call to action? Will we use it to fight? Or will we use it to give up?”

This is the longer version of Mike Ryan’s remarks (video):

The principle underlying a pandemic is a principal that in some senses the disease has reached a point where it is further spread from country to country, cannot be controlled…If this was influenza, we would have called it ‘pandemic’ ages ago because we know something inherently about the transmission dynamics of influenza. So it’s not an avoidance of the word. But the word is important...

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