The CDC is investigating a possible link between EV-D68 and clusters of unexplained paralysis in children. A California doctor who has investigated similar cases of mystery paralysis sees a connection.

Hospitals in at least two states have reported pediatric patients with unexplained symptoms of paralysis that may be linked to the ongoing outbreak of enterovirus D68 (EV-D68).

At least 14 patients, all younger than 18, have been seen at Children’s Hospital Colorado and Boston Children’s Hospital with limb weakness and lesions in the gray matter of their spinal cords. The New York Times has reported a handful of additional cases in Colorado, Missouri, and Michigan. Most of the children had recently experienced respiratory illness, suggesting a link to EV-D68.

Some of the young patients had drooping faces, double vision, and trouble swallowing.

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Most people infected with EV-D68 experience no symptoms. But 500 people, most of them children, have experienced respiratory illness caused by the virus.

One Rhode Island child infected with the virus died after also contracting a serious Staphylococcus infection. The CDC also found evidence of the virus in three other patients who died in September, but what role it played in their deaths remains unclear.

The virus is related to poliovirus, and its behavior may be more similar to polio than doctors believed. Like EV-D68, polio infects far more people than it sickens. In a fraction of cases, polio creeps into the patient’s nervous system, where it can cause paralysis.

The current paralysis cases are consistent with the idea that a small fraction of patients sickened by EV-D68 also develop neurological symptoms. The clusters of unexplained paralysis are occurring in areas that have recently seen clusters of respiratory illness due to EV-D68.

“That’s exactly what we think is happening,” said Dr. Emmanuelle Waubant, a neurologist at the University of California, San Francisco, who published research earlier this year suggesting that EV-D68 was linked to cases of a “polio-like” illness in California dating back about two years. EV-D68 was first identified in California in 1962, but infections have been rare.

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“In different states and also in Canada, we started seeing an increase in the number of those paralysis cases in the context of that increase of viral infections. And most of the patients we have seen with paralysis actually had preceding upper respiratory illness,” Waubant said.

The children’s symptoms are also unique.

“For most of these cases the paralysis is unusual compared to the type of paralysis we see often for other infections and in these specific infections,” Waubant said.

But the connection between EV-D68 and paralysis is not clear cut. Just four of the Colorado paralysis patients have tested positive for EV-D68, according to Children’s Hospital Colorado.

There were no reports of EV-D68 in their spinal fluid, where it could cause the lesions. But Waubant, at least, doesn’t think that rules it out as the culprit.

The virus is difficult to detect in spinal fluid, she said. And if patients are tested weeks after their symptoms appeared, they may have already cleared the virus from their systems.

The hospitals have ruled out other potential causes for paralysis, such as West Nile virus and Lyme disease, according to the CDC. In Colorado, at least seven of the patients were also confirmed to have the appropriate polio vaccinations.

If the patients in Colorado and Massachusetts progress like the earlier California cases, some will improve on their own and others may experience permanent partial paralysis.

“This is a paralysis that can last,” Waubant said.

Doctors recommend that parents seek immediate medical care if children have trouble breathing, slur their speech, or experience double vision.

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