A distinctive barking cough that sounds like a seal, appearing suddenly in the middle of the night — this is how most parents first encounter croup. And right now, the virus responsible for it is circulating at elevated levels across the United States.
The CDC's June 22, 2026 respiratory data update confirmed that parainfluenza virus (PIV) is elevated nationally. PIV is the leading cause of croup — a respiratory infection that causes inflammation and swelling in and around the voice box and airway, producing the characteristic barking cough and, in more severe cases, a high-pitched breathing sound called stridor.
