What Is a Pandemic, Anyway?

It’s a massive outbreak of disease—but what deserves the distinction might surprise you.

(Photo: Getty Images)

Apr 2, 2015· 1 MIN READ
Vince Beiser has reported from more than two dozen countries for Wired, Harper’s, The Atlantic, Rolling Stone, and others. In 2014 he won the Media for Liberty Award.

Ebola may have become the world’s most infamous disease last year, but it’s far from the most lethal. It doesn’t even qualify for that scariest of medical terms: pandemic.

If a killer like Ebola doesn’t rate that classification, what does? The flu, for one. We don’t think of the common ailment that way, but it’s just one of many diseases that fall under the category of “pandemic.” Though the term conjures up images of mass-scale death and devastation, it basically means any epidemic—i.e., an outbreak of disease—that spreads across a large, multinational area.

For a disease to spread so broadly, it needs to be easy to catch. That’s why various strains of flu are prime candidates for creating pandemics. Airborne viruses can be transmitted rapidly from person to person, spreading exponentially. In our globalized age, travelers often inadvertently help spread them around the region and the world.

Most people who get the flu recover easily. But because it affects such huge numbers of people, it’s also a major problem, especially for the very young, the elderly, and the infirm. In the U.S. every year on average, 5 percent to 20 percent of the population gets the flu, and more than 200,000 people are hospitalized as a result, according to the Centers for Disease Control and Prevention. When a particularly virulent new strain of flu appears, the results can be catastrophic. The 2009 H1N1 influenza pandemic, for instance, killed an estimated 284,000 people worldwide—most of them in the developing world.

What Is A Pandemic?

Diseases that are acquired through contact with an infected person’s bodily fluids—such as Ebola—tend to spread less easily than those you can catch just by breathing the wrong air. “Ebola, although we’ve seen isolated cases in Europe and 
the U.S. and it’s affecting a rather large area in West Africa, is an 
epidemic, not a pandemic,” says Theresa Macphail, a medical anthropologist at Stevens Institute of Technology. “Thankfully, because of the need for direct 
routes of transmission, Ebola poses a very low pandemic risk.”

Still, blood-borne diseases can become pandemics. HIV/AIDS is the prime example. Worldwide, some 35 million people are living with the virus, and 1.5 million die of it each year.

There are also pandemics that sicken people without killing them. Chikungunya, a mosquito-borne virus first spotted in Tanzania, has spread across Africa and Asia and, in recent years, into Europe and the Americas, according to the World Health Organization. It rarely kills, but it causes debilitating joint pain that can last for weeks.

If that’s not enough to worry about, “the old bugs that caused widespread epidemics—cholera and T.B., for 
instance—are also still with us,” Macphail says. “And with increasing microbial 
resistance, they may pose just as big of a threat to our future as they 
did to our past.”

This article was published in connection with Fortitude, the new drama series set in the Arctic Circle that uncovers the unintended consequences of climate change and infectious diseases. An all-new episode of Fortitude premieres tonight at 10 p.m. ET/PT on Pivot TV, our sister network.