An acute infection of the tracheobronchial tree caused by Bordetella pertussis, a bacteria species exclusive to infected humans. The disease (also known as pertussis) follows a prolonged course beginning with a runny nose, and finally develops into violent coughing, followed by a slow period of recovery. The coughing stage can last 2–4 weeks, with a whooping sound created by an exhausted individual rapidly breathing in through a narrowed glottis after a series of wrenching coughs. The classical disease occurs in children 1–5 years of age, but in immunized populations infants are at greatest risk and adults with attenuated (and unrecognized) disease constitute a major source of transmission to others.