Between attacks the patient may seem fine. In the convalescent stage, lasting 1-2 weeks, episodes decrease in frequency and severity. Cough, however, may persist for several months. Infants may present with apnea only. Complications of pertussis can be life threatening.
Otitis media is common.
Convulsions and coma related to anoxia can occur. Differential diagnosis includes other respiratory viruses including adenovirus, parainfluenza viruses, respiratory syncytial virus as well as mycoplasma. According to the CDC, a clinical case definition is appropriate for endemic or sporadic cases. However, there may be no lymphocytosis in very young infants, vaccinated children or with mild disease in adults. Although drug therapy does not shorten disease, it will eliminate nasopharyngeal carriage and thus reduce the likelihood of transmission to susceptibles.