Older children or adults often have no symptoms or will only have mild symptoms such as a nagging cough. These older persons with infectious pertussis can transmit to other unprotected persons, especially infants.
The symptoms of pertussis occur in phases. The first phase, which lasts one to two weeks, is usually with mild upper respiratory symptoms (cold like symptoms with occasional mild cough). During the second phase, which lasts one to six weeks, the cough can progress to severe spasms often with the characteristic respiratory whoop, followed by vomiting. Fever is minimal. Older children and adults may have persistent cough with no whoop. During the third phase, which can last for several months, there is gradual reduction of the coughing spasms. Generally, the duration of pertussis is six to 10 weeks with more than half of the cases lasting less than six weeks.