Another 29 cases were reported today in the nationwide outbreak of enterovirus D68 (EV-D68) respiratory infections in children, and one of the outbreak strains is closely related to a strain that was associated with polio-like illness in a few California children in 2012, according to the Centers for Disease Control and Prevention (CDC).
The outbreak count grew today to 472 confirmed cases in 41 states and Washington, D.C., from 443 cases in 40 states and Washington yesterday, the agency reported. The new state on the list is New Hampshire. All but one of the cases have been in children.
It's not clear whether the outbreak has peaked yet, Mark Pallansch, PhD, director of the CDC's Division of Viral Diseases, told CIDRAP News today. He said cases are increasing in some areas and declining in others.
"We don't have a clear picture as to whether there's a trend at this point, he said. "It's still enterovirus season, so it's not surprising."
The virus, which was fairly rare in the United States until recently, causes cold-like symptoms but can lead to serious breathing trouble, especially in children who have asthma, the CDC says.
Link to 2012 California case
The CDC and Colorado officials recently reported that four of nine Colorado children with a polio-like illness tested positive for EV-D68, and yesterday Colorado officials reported a 10th child with a similar condition. Most of the children had a febrile respiratory illness in the 2 weeks before their neurologic symptoms appeared.
In February, doctors in California reported five mysterious polio-like cases in children that had been reported to a state neurologic surveillance system from August 2012 to July 2013. Three of the children had a preceding respiratory illness, and two tested positive for EV-D68.
Pallansch reported today that an EV-D68 genetic sequence from one of the California cases "does match the current major outbreak strain. However, there are at least five different strains that are circulating in the US. So it isn't like influenza where there's a single type that's circulating; it's multiple different strains with different linkages in the past."
He said the California strain that's linked to the current outbreak strain dates to 2012. "We know of two other sequences they've obtained from earlier years that are not linked to the current outbreak but are more linked to the one that occurred in 2009 and 2010 in Philadelphia," he added.
"The viruses currently [circulating] are also linked to viruses we saw in 2013, so these have indeed been around for multiple years," Pallansch said. "Given very limited surveillance, we can't really conclude much more than that."
He said he had no new information on the investigation into the Colorado cases, other than that a 10th case has been reported.
The latest case-patient, like the other nine, is at Children's Hospital Colorado in Denver, the Denver Post reported yesterday, quoting Larry Wolk, MD, MSPH, director of the Colorado Department of Public Health and the Environment.
The story said the nine children were originally diagnosed as having myelitis, an infection of the gray matter of the spinal cord, and eight of them were tested for viruses. Four tested positive for EV-D68, and the other four tested positive for a rhinovirus or another enterovirus. The story said officials gave no information on test results for the 10th patient.
Doctors at a press conference emphasized that it remained uncertain whether the children's muscle weakness is connected to EV-D68, according to the Post.
Joyce Oleszek, MD, who specializes in pediatric rehabilitation medicine, said none of the children had completely lost the ability to move, but had varying degrees of muscle weakness; difficulty swallowing, breathing, and walking; and weakness in the neck and trunk, the newspaper reported. She said it was too early to know whether the problems will be permanent.
Another official said Children's Hospital Colorado saw 4,021 children with severe respiratory illness between Aug 18 and last weekend, and about 10% of them were admitted, according to the story.
CDC list of states with confirmed cases
CDC EV-D68 page
Sep 30 Denver Post story
Sep 29 CIDRAP News story "EV-D68 cases jump to 443 as neuro illnesses probed"
Related Feb 24 CIDRAP News story on California cases