Seven facts and a mystery about hand, foot and mouth disease

Coxsackie, N.Y. exit sign

Named for a town in upstate New York, coxsackievirus is one of the culprits behind hand, foot and mouth disease, a common childhood illness.

profvrr/Flickr (CC BY-NC-SA 2.0)

A few days ago, Baby V came down with a bug. Her nose ran, her appetite disappeared and her little body radiated heat. Over the course of a rough night, mean red spots cropped up on the sides and bottom of her feet. A little later, we found similar blisters on her hand. And then, as veteran parents might have suspected by now, we saw blisters around her mouth. Her rash eventually spread, but that initial pattern cinched the diagnosis, our doctor told us: Hand, foot and mouth disease.

Not to be confused with the foot (hoof) and mouth disease that afflicts cows, sheep and pigs, hand, foot and mouth disease is a common childhood ailment caused by a handful of different viruses. Because the disease spreads like wildfire in day cares, playgrounds and pools, most kids get infected before they’re 5.

HFMD is caused by a virus, so there’s not much to do other than ride it out. This lull gave me ample time to become a bit of a HFMD hobbyist, and given the rash of breakouts reported so far this summer, my reading material has been plentiful. Thus, I offer you seven facts and a mystery about this nasty disease:

Sadly, you can get HFMD more than once. Most of the time, the culprit is either coxsackievirus A16 or enterovirus 71. But other viruses can cause HFMD misery, too. Coxsackievirus A6 can wreak havoc on children with its high fever and unusual rash. During outbreaks of coxsackievirus A6, “we saw a lot more kids with blisters than what was usually expected,” says Eileen Schneider, a medical epidemiologist at the Centers for Disease Control and Prevention in Atlanta.

And a new subgroup of enterovirus 71 has been spotted in mainland China and Hong Kong. Viral variety means that having HFMD once doesn’t mean you’ll never get it again. Depending on the similarities of the viruses, a previous exposure might help your body fight off the new infection, but it’s no guarantee.

Like lots of other viruses, enteroviruses like it warm. That means that infections are more common in the south. In cooler climes, infections show a more cyclical pattern, peaking in summer and early fall.

An HFMD vaccine against enterovirus 71 is in the works. Inactivated forms of the virus showed strong protection in a study of thousands of Chinese children. The vaccine won’t protect against HFMD caused by coxsackieviruses, though.

These highly contagious infections can spread through secretions such as saliva and feces. Those bodily effluents are loaded with virus because it replicates in the mouth, throat and GI tract. Blisters can contain viral particles, but oozing vesicles aren’t thought to be a major source of transmission, says Tom Solomon of the University of Liverpool in England.

Don’t be completely surprised if fingernails fall off post-infection. It can happen.

The viruses stick around in the body for a long, long time. Coxsackievirus A16 has been found in the stool of infected children for six weeks. Enterovirus 71 can last for 10 weeks. Contagion diminishes during this time, and people argue about just how long children ought to be sidelined. Different doctors have different answers, as I’ve learned in my completely non-scientific poll of local pediatrician responses. Our pediatrician told us that Baby V could safely return to society about two days after her fever was gone. Another friend’s pediatrician said that the blisters all need to be gone before the kid went out in public. And yet another friend heard that contagion is gone as soon as the fever lifts. “There’s no magic number” of days that people are contagious, says Schneider. The best thing to do is to look at each child’s symptoms and use your best judgment.

If you’ve ever driven north on the 87 out of New York City, you’ve probably passed Coxsackie, the upstate New York town that provided the fecal samples that harbored the newly discovered coxsackievirus.

And finally, a puzzler: The reason that the viruses cause mayhem on hands, feet and mouth — and not elsewhere in the body — remains a mystery, at least to me and the virologists and pediatricians I asked. “I don’t think anybody knows for sure,” Solomon says. It’s possible that lesions in the mouth and throat might enable the virus to spread more effectively through a cough, Solomon says, but hand and feet blisters “might just be a quirk of the virus.” I’m eagerly awaiting answers, so please chime in if you have a guess. I’ll update this post if someone can solve the mystery.

Laura Sanders is the neuroscience writer. She holds a Ph.D. in molecular biology from the University of Southern California.

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