These bacteria produce a potent toxin that inflames the respiratory tract and that prevents the cilia from functioning properly. The disease can be serious or fatal in infants and unimmunized children. It is much milder in teens, adults, and in immunized children - but still can be a real nuisance. As you might guess, it can be far worse in people with asthma or with immune deficiencies. For the next 1 to 2 weeks, pertussis is not unlike a cold.
People have runny noses, sneezing, and perhaps a low-grade fever.
A mild cough begins that gradually worsens. The worst part of the illness lasts from 1 to 6 weeks. Spasms or attacks of coughing may come up to 15 times per day. Even so, young infants will often turn blue with the spells from lack of oxygen. The mucus is often thick and sticky.