What Is A Pandemic Anyway?

This pandemic word has been getting tossed around a bunch in the media lately. Ever since the World Health Organiztion started raising the pandemic alert level back in April of 2009 the media started tossing the P word out there like it was a bad cliche or a Geiko commercial. But what is a pandemic anyway? What makes one disease a pandemic and another one a run of the mill epidemic?

To answer that question lets start with that other, over-used media phrase “epidemic“.

Epidemics are all about predictability. (Not rate of spread or numbers of individuals effected.) So lets say you’re a run of the mill influenza virus and you’re off doing your seasonal influenza thing. The Centers for Disease Control may predict that you’ll infect 8.2-12.9% of the population this year.

To become an epidemic you need to beat your numbers. You need to outperform your statistical curve. Step up big time and infect 14% of the population and you too may be granted the status of “flu epidemic”.

Pandemics are a bit different. Pandemics need to meet a few more criteria before they get dubbed pandemic.

First, they need to be new.

Since they’re new, it’s difficult to predict how far or fast they will spread, so the epidemic predictability thing goes out the window. If you’re already a known virus that has existed in the population before, you’re days of pandemic potential are over. Only the rookie viruses get to compete.

Second, they need to be contagious among humans and pose a serious health risk.

Cancer is widespread, but it isn’t a pandemic because it isn’t contagious. It doesn’t spread from human to human so it isn’t in the running. Some minor common cold viruses can be widespread but don’t pose a serious enough health risk to be considered for pandemic status.

Third, they need to be contagious enough to spread sustainably in large populations.

This is why pandemics almost always involve multiple countries and entire continents. In today’s world of advanced transportation, most viruses need to demonstrate that they can spread around the globe before being considered for pandemic status. If the virus can’t make the ride on a 747 from New York to London it isn’t going to make the grade. H1N1-2009 was widespread in 70 countries before it was declared a pandemic.

So there you have it. Unfortunatey, we’re going to hear these terms used more and more in the media. Now you know what they really mean.