3 year old coughing over 3 weeks, sounds like a whopping cough, he was treated for a viral infection a month ago but coughing won't stop?

Maybe: A cough is the bodies way of removing debris from deep within the lung. Some viral infections will produce a cough and or wheezing that can persist for a month. Whooping cough is well known for a staccato like cough with repeated cough followed by a deep inhale or whoop. That cough has been labeled the "100 days" cough in many descriptions.