Authorities are warning of an infection that's been circulating among babies in the U.S. Called parechovirus (PeV), it can cause severe illness in very young infants.

The Center for Disease Control and Prevention (CDC) has been receiving reports of PeV in "neonates and young infants" in multiple states since May, the agency said in the Health Alert Network (HAN) health advisory it issued Tuesday.

The alert aims to inform doctors and health departments that the virus is "currently circulating" in the U.S., the agency noted. As such, health care providers are encouraged to consider PeV when diagnosing infants that are presenting symptoms like fever, a "sepsis-like syndrome" or neurologic conditions such as seizures and meningitis.

A newborn, identified by the name Ronan, is said to have died from PeV in Connecticut, WTNH reported. According to baby Ronan's parents, he started to be "very angry" and cry "a lot" when he was just 20 days old. He also had redness on his face and chest and soon began having seizures that eventually became difficult to control. He died when he was just 34 days old.

However, how the 2022 cases match up to cases in "previous seasons" remains "unclear." This is because "there is presently no systematic surveillance for PeVs in the United States," the CDC said.

What Is Parechovirus?

Human PeVs are "common childhood pathogens" that are from the same family as enteroviruses, which cause many childhood infections. According to the CDC, among the four PeV species, only PeV-A is known to cause illness in humans. And among the PeV-A types, PeV-A3 is the one that's mostly linked to severe cases.

"To date, all PeV positive specimens tested and typed at CDC were type PeV-A3," the agency explained.

PeV can be transmitted via contact with the breath, saliva or feces of someone who's infected, HealthDirect noted. This is regardless of whether the person is symptomatic or not. People may also get it by touching contaminated objects. This is why it's important for those who are sick to practice good hygiene to help prevent its spread.

It can manifest mild symptoms or no symptoms at all but may also cause severe illness.

"Symptoms such as upper respiratory tract infection, fever, and rash are common in children between 6 months and 5 years, with most children having been infected by the time they start kindergarten," the CDC said. "However, in infants less than 3 months, severe illness can occur, including sepsis-like illness, seizures, and meningitis or meningoencephalitis, particularly in infants younger than 1 month."

Other symptoms to watch out for in babies and younger children include diarrhea, fast breathing, irritability, "floppiness," drowsiness, seizures and "extreme tiredness," Healthdirect noted.

So far, there is no "specific treatment" for PeV.