Pertussis can cause violent and rapid coughing, over and over, until the air is gone from the lungs and you are forced to inhale with a loud "whooping" sound. These coughing jags can trigger the gag reflex causing you to throw up, and make you very tired afterward. The "whoop" may not be present, and the illness tends to be less severe, in teens and adults. This is especially true in those who have been vaccinated. Because pertussis in its early stages appears to be nothing more than the common cold, it is often not suspected or diagnosed until the more severe symptoms appear. Infected people are most contagious during this time, up to about 2 weeks after the cough begins. Antibiotics may shorten the amount of time someone is contagious.
Although you are often exhausted after a coughing fit, you usually appear fairly well in-between. Coughing fits generally become more common and severe as the illness continues, and can occur more often at night. The coughing fits can go on for up to 10 weeks or more. In China, pertussis is known as the "100 day cough." Recovery from pertussis can happen slowly. The cough becomes less severe and less common. However, coughing fits can return with other respiratory infections for many months after pertussis started.