Whooping cough wave is still accelerating nationwide. Here's what to know about symptoms and treatment.

A wave of whooping cough infections is continuing to worsen nationwide, data from the Centers for Disease Control and Prevention suggests, with weekly reported cases now accelerating to the highest levels seen in the U.S. for years. 

At least 259 pertussis cases were reported during the first week into August, the CDC now tallies, up from 215 weekly cases towards the end of June. 

Pennsylvania has reported 1,489 cases so far this year, the most of any state. New York has reported the next largest total of cases, at 1,266 infections.