Multiple health systems are now reporting a potential uptick in serious cases of parechovirus infections in infants, after cases largely disappeared from children's hospitals during the COVID-19 pandemic.
A new report published by the Centers for Disease Control and Prevention documents how cases have increased at one medical center in Tennessee, which has already hospitalized 29 cases so far this year, including 23 infants in a six-week period.
That marks an increase from previous years: only 19 cases were detected over five months in 2018.
While parechoviruses commonly infect children, triggering only mild symptoms in many kids, the virus can lead to severe disease when infecting babies younger than three months old. Some develop sepsis-like symptoms or central nervous system infections. It can also raise the risk of longer-term developmental problems.
So far, at least 21 of the babies have recovered. One child is expected to face "severe developmental delay" after "persistent seizures."
The findings from doctors at Vanderbilt University Medical Center and Tennessee's health department were published on Thursday in the CDC's Morbidity and Mortality Weekly Report.
Fever, fussiness, and a low appetite were the most common symptoms among babies admitted in the study.
It follows a health alert issued by the CDC earlier this month, which warned of multiple states reporting parechovirus infections of newborns and young infants. It comes as pediatric infectious diseases doctors around the country have been probing a potential uptick in cases.
CBS affiliate WFSB-TV reported earlier this month on a family mourning the death of a baby in Connecticut, after the baby suffered seizures from his infection.
Is there really an uptick in cases? "This is not normal"
"In the community, some doctors started discussing in our infectious disease forums, 'hey, we're seeing more of these cases, are you seeing more of this?' And yes, we, several institutions around the country, we're seeing a lot and this is not our usual," said Dr. Cristina Tomatis Souverbielle of Ohio's Nationwide Children's Hospital.
Tomatis Souverbielle co-authored a study published last year that routinely tested infants in multiple parts of the body, including spinal fluid and the blood, looking for parechovirus. They have seen around 20 cases, starting mostly around June, so far this year.
Many other health systems have only recently scaled up their testing for parechovirus infections, which can be expensive and are performed by a handful of laboratories. There is also no systematic national surveillance in the U.S. for parechovirus, the CDC says.
"Some doctors were arguing, well, maybe it's because we're testing more and we didn't know. But I think we knew from before, we were testing before, and this is not normal," said Tomatis Souverbielle.
Parechoviruses are believed to generally circulate in the summer and fall. Tomatis Souverbielle's hospital saw a similar trend, but also turned up cases in every month of the year.
Most children have likely survived parechovirus infections with few or no issues by kindergarten, the CDC says, which can be spread through respiratory symptoms for weeks and via stool for months.
"They outnumber enteroviruses, which are well known to pediatricians as a cause of summer meningitis to little infants. Parechoviruses are the most common important viral pathogen that affects the central nervous system in babies, bar none," said Dr. Mary Anne Jackson, dean of the University of Missouri-Kansas City's school of medicine.
Are we seeing more parechovirus because of COVID-19?
Jackson's hospital – Children's Mercy-Kansas City – is also among those that have been regularly testing for and researching the virus for years in young infants in the hospital with potential symptoms.
Jackson shared surveillance data tracking the hallmark every-other-year pattern of circulation of the virus since 2006, peaking at 62 cases admitted to the hospital for the whole year of 2018.
But that pattern broke as the COVID-19 pandemic swept the country in 2020, with virtually no cases over months when they would have expected to see a wave of infections.
Now parechoviruses appear to be circulating once again, infecting young children at a potentially faster clip than have been seen in previous years. Jackson's hospital has seen 25 so far this year.
"Obviously, in the next two to four weeks, I expect we'll see more cases, especially if our numbers keep going down for COVID and keep going up for parechoviruses, because August is a big season for this virus," said Jackson.
Tomatis Souverbielle said that scientists are exploring a variety of theories as to why transmission may be higher this year, in the wake of the COVID-19 pandemic. The easing of pandemic restrictions may have simply led to more spread of parechovirus, as families began mingling again.
"There's also a theory that, because kids have not been exposed to it in the past few years, now they're being more exposed and are more susceptible to this," said Tomatis Souverbielle.
How are parechovirus cases treated in babies?
The CDC says that to date, all parechovirus cases investigated by the agency have been a specific type of the virus known as PeV-A3. This type of the virus, which has made up the majority of "typed" parechoviruses in some previous studies, is also the one most often linked to severe cases.
Diagnosing an infant with parechovirus can help doctors in managing the infections, including avoiding unnecessary testing and ending the use of antibiotics that may have been started before a bacterial infection could be ruled out.
However, there are no specific antiviral drugs approved to treat these infections.
"The fact of the matter is, there is not a treatment. Babies can get better on their own. All the treatment is supportive. So it's IV fluids, it is fever control, it is seizure control for babies who present with seizures," said Jackson.
Jackson said informing parents of their baby's diagnosis can also help them over the coming years as they monitor their child's development.
A growing body of research suggests a minority of children who survive the disease as babies may end up with neurodevelopmental delay as they get older, which may warrant early intervention by their school and parents.
Those developmental issues cannot always be predicted with how severe the initial disease was, Jackson said.
"We do know that affected babies, sometimes they're impaired, but sometimes they're completely normal. And the babies who were not significantly impacted by their early infection, some of those babies did not seem to be doing completely normally developmentally," said Jackson.
Correction: This story has been updated with the full name of Dr. Cristina Tomatis Souverbielle.
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