CDC Issues Parechovirus Warning—Here's What PeV Can Look Like in Infants

Fact-checked on July 15, 2022, by Marley Hall, a writer and fact checker specializing in medical and health information.

Parechovirus, a virus that in rare cases can be life-threatening for young infants, is circulating in multiple states, the Centers for Disease Control and Prevention (CDC) announced on Tuesday.

In the advisory, the CDC urged medical professionals to keep an eye out for the disease when treating newborns and babies under 12 months of age who are showing signs of severe illness.

Parechovirus is a fairly common virus that circulates every year in the summer and fall, Claire Bocchini, MD, an infectious disease specialist at Texas Children's Hospital, told Health. In fact, she said it's estimated that most people have been exposed to the parechovirus by the time they enter kindergarten.

But the CDC specifically pointed to reports of more cases of parechovirus type 3, which is why they're raising the alarm.

"Unfortunately, we're seeing disease from the parechovirus species A type three (PeV-A3), which has been associated with more severe disease in infants," Dr. Bocchini told Health. "It's a type of virus and a very common family of viruses [that] circulates every year. And we just seem to have more of this one type that is causing more severe disease this year."

Signs and Symptoms of Parechovirus in Infants

For most people who are infected with parechovirus, the symptoms are incredibly mild.

"In older children—children who are 2, 3, 4, 5—you usually have no symptoms, or you can have upper respiratory symptoms—runny nose, sometimes cough," Dr. Bocchini said. "Sometimes you can have some gastroenteritis with diarrhea."

Parechovirus is part of a group of viruses called enteroviruses, according to Ian Michelow, MD, FCPaed, the division head of pediatric infectious diseases and immunology at Connecticut Children's Hospital. This family of viruses usually causes very mild illnesses—some are responsible for hand, foot, and mouth disease, for example.

"The other types of viruses that are in the same family will cause skin infections or rashes, or they can cause respiratory illnesses, or maybe some gastrointestinal illnesses like stomach bugs, diarrhea, vomiting," Dr. Michelow told Health. "It's the rare exception that children get much more severe disease, and it's typically in very young children."

For those infants, however—usually 3 months old or younger—a brush with parechovirus, especially PeV-A3, can be much more dangerous, mostly because their immune systems are not fully developed.

"What it can cause in infants is fever and sepsis, which is kind of like an overwhelming inflammatory reaction to an infection that in itself can be damaging to the body," Kristin Moffitt, MD, an associate professor in the pediatric division of infectious diseases at Boston Children's Hospital, told Health. "Particularly it can infect the central nervous system of very young infants, and could be associated with seizures."

Babies with parechovirus can also experience brain swelling, or encephalitis, Dr. Michelow said. The liver and heart can also be affected, Dr. Bocchini added.

Because infants this young can't point to specific symptoms they're feeling, parents have to be on the lookout for any signs that their child is suffering from a more severe case of parechovirus, rather than a more common mild one.

"This would be a baby who is not feeding, stops feeding well, a baby who's floppy or maybe has abnormal movements, which could indicate seizures, or a baby who has a high fever," Dr. Michelow said. "A baby with a mild illness may be able to console when the mother is nursing. But in these babies, because they may have an infection of the brain, they are not easily placated and consoled. So they get very irritable."

There's no specific antiviral treatment for parechovirus, so all the hospital staff can do is diagnose what's causing the baby's severe symptoms, make them more comfortable, and keep them hydrated, Dr. Michelow said. Even despite the severe symptoms and lack of antiviral treatment, he said, the majority of babies admitted to the hospital recover. Only a very small number of cases are fatal.

"In the past month, I've personally diagnosed and treated three babies [with parechovirus]. We did have infections cause encephalitis," Dr. Michelow said. "We proved what the diagnosis was, and these babies did extremely well. They had no problems and they recovered really within a few days."

Whether a young infant will develop severe or life-threatening symptoms from the parechovirus isn't entirely known. It can certainly depend on whether they get infected with the more mild, type 1 strain, or if they get sick with PeV-A3. Dr. Michelow also guesses that those infants who don't get as sick from the parechovirus may have received some level of passive immunity from their mothers while they were in the womb. Unfortunately, there's no way to know which infants might have some built in immunity against the virus–taking preventative measures is the best solution.

Keeping Your Family Safe From Parechovirus

Because there are no antiviral treatments or vaccines, the best way to keep infants safe from parechovirus is to rely on the preventative strategies that we're now comfortable with, thanks to the COVID-19 pandemic—washing hands, staying away from infants when you're sick, or maybe even masking up, Dr. Michelow said, especially for the first couple months of a baby's life.

The parechovirus is fairly contagious, and it can pass from person to person through stool or through respiratory droplets, like cough or saliva, Dr. Bocchini said. So these strategies help make sure that infants are as protected as they possibly can be.

And though the prevention strategies are similar, the CDC alert is not suggesting that there's a parechovirus epidemic in our future. Rather, it's just a heads up to parents and health care providers to be extra vigilant about the parechovirus, not to panic, Dr. Moffitt, Dr. Bocchini, and Dr. Michelow all agreed. In fact, the CDC said that a higher number of reported cases may not even be all that out of the ordinary.

"There are fluctuations from year to year with these particular viruses and other viruses," Dr. Michelow said. "So it may just be now that we are seeing a natural fluctuation and more frequent cases because it happens to be a year with more of these types of viruses."

Dr. Bocchini also notes that lots of viruses are circling in higher numbers right now because there was no normal transmission and building up of immunity during the first months of the COVID-19 pandemic. These higher numbers of parechovirus could just be a flare up as people start relaxing COVID precautions. It's too early to know for sure though, she said.

Besides the possibility that this is just a season with a higher swell of parechovirus, diagnostic testing has also greatly improved in the last decade, Dr. Moffitt said. In years prior, an infant coming in with a severe fever or sepsis may not have been diagnosed with the parechovirus. The CDC mentioned this in their warning—the higher numbers of parechovirus cases may be a result of better testing.

"It's just in the last few years that availability of especially PCR-based testing, or it's also called molecular testing, has really expanded our ability to diagnose the pathogenic cause of these infections," said Dr. Moffitt. "We're not sure how different this is from typical seasons, because we really have not had the same similarly widely available diagnostics as we have in the last few years."

Reports like the CDC's though will get the word out to parents and medical providers, and encourage them to be more aware of the Parechovirus, Dr. Bocchhini said.

"Right now, it's not mandatory reporting for this infectious disease," she said. "And with more reporting, we can get a better idea of how this virus circulates every year and have more information about it."