The Washington PostDemocracy Dies in Darkness

Americans bite each other literally all the time, data show

The undead make their way along Sligo Avenue during the annual Zombie Walk on Oct. 26, 2013, in Silver Spring, Md. (Bill O'Leary/The Washington Post)
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The Internet is abuzz today over news that a passenger on an Aer Lingus flight from Lisbon to Dublin grew agitated, bit a fellow passenger and then died after being restrained. Police are investigating, but Internet sleuths have already cracked the case: zombies, obviously.

Is it time to stock that bunker, grab your guns and head for Montana? Not quite. As it turns out, people attack and bite each other all the time. In the United States alone, in 2012 nearly 42,000 people took a trip to the emergency room after being assaulted and bitten by another human being. That's according to emergency department data maintained by the Agency for Healthcare Research and Quality within the Department of Health and Human Services.

To put it another way: You're over 10 times as likely to get bitten by another person as by a rat — even in New York. Also 10 times more likely to get bitten by a person than by a non-venomous snake or lizard. Other random animals — like cats and horses and cows and such — are about twice as likely to bite you as a human. Dog bites, on the other hand, are nearly 10 times as likely as human bites.

In 2012, there were no zombie bites recorded in HHS data.

Out of the 134 million or so ER visits in the United States in 2012, 41,710 involved a biting assault by another human being, according to these numbers. Men (52 percent) are slightly more likely than women (48 percent) to get bitten by another person. And the overwhelming majority of the cases — 74 percent — involved people between the ages of 18 and 44.

On the one hand, 42,000 bite victims may sound like a lot of people. That represents roughly 114 bites per day, or nearly 1 biting assault every 12 minutes! But in a country with 315 million people, assaults happen all the time. Human bites only accounted for about 0.03 percent of all ER visits in 2012, according to these figures.

One important data caveat: These figures don't include accidental human bites. HHS has numbers for these — there were about 30,000 of them in 2012 — but in the ER database there's no way to tell if a case was coded as both an accidental and purposeful bite. So I'm just focusing on the purposeful bites out of caution and also because what we're really interested in are instances where people are biting each other deliberately — not accidents from say, kids horsing around.

The HHS data don't give us much information about the circumstances around these instances, but several studies have been done over the years that shed some light. A 2007 review of 388 human bite cases found that roughly half of the bites occurred on the hands or fingers. Another quarter happened on the arms and legs, 18 percent were on victims' heads and necks, and 8 percent were "closed fist" injuries, where a person punched someone else in the mouth and hurt their own hands in the process.

And as it turns out, common back-alley brawls are likely a source of many human bite injuries. A 2007 report on severe human bite injuries referred to a plastic surgery center in Ireland suggested that "late night alcohol fueled aggression" — bar fights, in other words — accounted for roughly 86 percent of these cases. The majority (70 percent) occurred on the weekend or during public holidays.

Doctors have long known that human bites present a particularly nasty infection risk — not from zombie plague, but from the 700 or so species of bacteria that can typically be found oozing around in your mouth.

So, in conclusion: Yes, a passenger biting somebody on a plane and then dying does indeed sound like the opening scene of a zombie apocalypse film. On the other hand, people have been biting people for as long as people have existed, with no apocalypse to show for it.

At least, not yet.