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Why the mysterious, new enterovirus outbreak is baffling experts

A 13-year-old recovering from enterovirus D68 at Rocky Mountain Hospital for Children in Denver.
A 13-year-old recovering from enterovirus D68 at Rocky Mountain Hospital for Children in Denver.
Cyrus McCrimmon/Denver Post

Researchers first discovered enterovirus D68 in 1962. Since then, it's only caused tiny and sporadic outbreaks — until this year.

Right now, more than 500 children in 43 states have become infected, some landing in hospitals with severe respiratory infections. Known as EV-D68, the virus has also been linked with four deaths, and this week, the Centers for Disease Control and Prevention determined that it actually caused the death of one New Jersey four-year-old. This was the first-ever confirmed fatality in what is believed to be the largest-ever outbreak of the virus.

Enteroviruses circulate every fall and winter — often causing "summer colds" — though this strain of the virus is thought to be rare, leaving parents and health officials with more questions than answers. I spoke with Dr. Alfred DeMaria, the medical director and state epidemiologist for Massachusetts. He's been tracking the virus since the summer. What follows is a transcript of our conversation, edited for length and clarity.

Julia Belluz: There are many worried parents across the United States right now, especially after the death of a four-year-old from the virus and the speculation that it could cause paralysis. What advice do you have for them?

Alfred DeMaria: This virus may cause these complications in a very small proportion of people infected. These are terrible complications but in most kids, this doesn't happen. Parents should do everything possible to prevent respiratory infections in the first place: hand washing, coughing into the sleeve, good hygiene.

In Hong Kong in 2003, when they had the severe acute respiratory syndrome (SARS) outbreak, they made the same hygiene recommendations to prevent transmission of SARS and they saw a 90 to 99 percent decrease in other respiratory viruses. This is proof of concept that these kinds of things — washing hands, coughing in your sleeve — do reduce transmission.

JB: When did you become aware of EV-D68?

AD: We became aware of this in mid-August when cases were being observed in the Midwest. I called all the pediatric hospitals in Massachusetts and they weren't seeing anything unusual. But in the beginning of September, there was abruptly this uptick of kids presenting with asthma. September is a bad month anyway because of the number of allergens in the atmosphere and the stress of going back to school, which tend to precipitate asthma. We tested about 140 kids and so far, 23 were positive for the virus.

JB: Enteroviruses typically circulate in summer and early fall. Are you seeing the case load increase or decrease now that we're well into October?

AD: Over the last couple of weeks, we've seen a drop off in respiratory infections. We're not seeing a lot of severe asthma, which was the indicator for enterovirus D68. So it seems to be on the wane.

JB: What symptoms do the kids who tested positive for the virus have?

AD: Sore throat, nasal congestion, cough, malaise, a headache lasting for three to seven days. It has been showing up in kids with asthma. Most of these kids didn't have a fever, but they had abrupt onset. Most of these kids got treated and released, even the ones that wound up in the ICU. Their infections were rapidly controlled. We made sure they all had an asthma treatment plan in place.

JB: What do you make of the links between enterovirus D68 and the more severe side-effects we're now seeing?

AD: The problem we're running into with the limb weakness is that, with the virus circulating, there are probably large numbers of children that have it on them. So if something else happens — and you find the virus in their noses — is it a coincidence or directly related? That's the difficulty. It may just represent a widely circulating virus that's in a lot of respiratory tracts so it makes it very difficult to determine cause and effect unless you find it in the spinal fluid or blood.

Right now, there's further testing to find that out. It's possible the limb weakness that's being observed is caused by EV-D68 because enteroviruses have this capacity to cause that kind of neurological disease. So far it hasn't been proven.

JB: Can adults become infected, too?

AD: Adults would have to have it, too. You wouldn't have the number of children infected if adults didn't have it.  But it's not striking them in the same way. They must have a more mild form of the disease.

JB: Any ideas about why this virus has come on so strongly this year?

AD: Almost every year, some enterovirus emerges. Usually, it's a different one each  year. This year it happened to be enterovirus D68. Enterovirus D68 was once called rhinovirus 87, which is a cause of the cold. So this virus typically behaves like the common cold. These viruses have the capacity to change over time. So this virus has that particular predilection for making an airway disease worse and now it may be causing this limb weakness.

JB: So we may be seeing some detection bias?

AD: In the past, it might have been circulating as a cause of a summer cold. But you'd have to test for it, and we didn't have the same kind of testing capacity that we have now until very recently. Now we're going to find a whole bunch of viruses that may or may not be rare because we have the capacity to test for them.

To learn more, see our Vox explainer: What we know and don't know about Enterovirus D68.

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