The Centers for Disease Control and Prevention is warning a virus that can cause severe illness or death in newborn babies is circulating in “multiple states” after it killed a baby boy in Connecticut. The parechovirus (PARE-co-VIRUS), or PeV, is common in children. According to the CDC, most kids will get it by the time they’re in kindergarten, but it can have grave consequences for infants younger than three months old. The virus can cause an upper respiratory infection, fever, and rashes in older kids between six months and five years old. But very young infants can have “sepsis-like illness, seizures, and meningitis,” the CDC says. Babies under one month old are the most vulnerable.