After virtually disappearing for several years amid measures aimed at curbing the spread of COVID-19, the Centers for Disease Control and Prevention is now urging doctors to be vigilant for a renewed wave of enterovirus D68, or EV-D68 — a viral infection in children that can cause a rare kind of paralysis.
In July and August, the CDC says hospitals detected an increase in infections caused by enterovirus D68. The number is now the biggest seen since 2018, when the agency tracked the last wave of summer and fall infections caused by the virus.
Many children are infected by enterovirus D68 early in their life and will face only a range of mild cold-like symptoms at worst, like runny nose and cough. One study in Missouri from 2012 and 2013 found antibodies from a prior infection in every child they tested.
But some kids, especially those with underlying conditions like asthma, are at higher risk of severe symptoms that can cause breathing issues and require hospitalization.
A small fraction of infected kids also develop a rare complication known as acute flaccid myelitis (AFM), which can result in muscle weakness and paralysis similar to, but likely rarer than, the paralysis caused by polio.
In 2018, there were 238 reports of acute flaccid myelitis to the CDC, which are believed to be largely caused by spikes in the virus. There's been no increase in such paralysis observed so far this year, the agency says. But as the virus spreads, there's growing concern that it's only a matter of time.
"Increases in EV-D68 respiratory illnesses have typically preceded cases of AFM, indicating that increased vigilance for AFM in the coming weeks will be essential," the CDC cautioned.
A CDC spokesperson said that reports can take up to a month to be added to the agency's acute flaccid myelitis tally, given the time it takes to review each patient's medical records. The agency is now working on weekly updates to the count, starting this Friday.
The federal alert, distributed Friday to doctors and health departments around the country, echoes a similar warning earlier this summer over a rise in cases of parechovirus in infants around the country.
Both viruses tend to spread in waves that fill children's hospital beds every other year. That was expected to happen in 2020, until the COVID-19 pandemic overtook them and disrupted the pattern.
"We wrote papers about how we should expect it to come back in 2020, and we were bracing and prepared for it, and lo and behold the whole world changes with COVID," recalls Dr. Kevin Messacar of Children's Hospital Colorado.
Modeling suggests an "immunity gap" in kids who haven't been exposed before may now raise the risk of a large outbreak of enterovirus D68.
"You have four years of children who now haven't seen those viruses and wouldn't be expected to have immunity to them," Messacar said.
Last year, scientists in Europe also voiced concern over the reemergence of enterovirus D68 infections after COVID-19 lockdown measures were eased across the continent.
Several reports of acute flaccid myelitis associated with the virus have since been reported in Europe, that study's corresponding author, Kimberley Benschop of the Dutch National Institute for Public Health and the Environment, told CBS News.
"However, as seen in previous EV-D68 peak years, where several EV-D68 associated AFM cases have been reported as well, we have not seen a major upsurge of these AFM cases in 2021," Benschop wrote in an email.
She added that health authorities were again alerting their doctors to be vigilant for a potential uptick in cases this year.
Enteroviruses are part of the same family of infectious pathogens as poliovirus and parechovirus, as well as rhinovirus – a close relative that also ranks as one of the most frequent causes of the common cold.
Enteroviruses are so closely related to rhinoviruses that they are "indistinguishable from one another" on most tests run by doctors, the CDC warns, and can be confused for each other.
"When EV-D68 is around, we need pediatricians, ER doctors, urgent care providers, to be on the lookout for this rare paralytic illness that can be associated with it," said Messacar.
Enterovirus D68 has been known to health authorities since the 1960s, when doctors uncovered it as the culprit behind a group of hospitalized children in California.
Efforts to track the virus ramped up after an outbreak in 2014 led to hundreds of children being hospitalized in the U.S., as well as cases of paralysis and deaths. Previous cases of acute flaccid myelitis and death in children have also now been linked to the virus.
That 2014 outbreak also began with hospitals warning the CDC in mid-August of "an increase in admissions of children with severe respiratory disease" that were eventually linked to the virus.
"Very similar to the prior waves, it's looking a lot like 2014 in children's hospitals right now," said Messacar.
Messacar, who is also an associate professor at the University of Colorado, had been working on research studies in 2014 when the outbreak began to swell.
He is now helping to lead a pilot study for the National Institutes of Health, launched last year, that hopes to study the virus as it spreads this year, in hopes of accelerating answers for the disease.
While no specific drugs are currently licensed to cure acute flaccid myelitis caused by the virus, doctors have several options for medications and techniques that might help improve patients' lives — especially if started early.
"Having watched these waves come through since 2014, for every one case that we see coming in right at the onset of paralysis, we always see a few that come in weeks or months later having other diagnoses," said Messacar.
There are also no approved vaccines or treatments specifically to target enterovirus D68, although early data suggests monoclonal antibody drugs might work to prevent and treat the disease.
"This is not 2014. We know more about what this virus does, how it does it, how to detect it, how to take care of these children better," Messacar said.