This disease is increasing in incidence in both children and adults.
Pertussis occurs most often in late summer and fall.
After a week or two, a persistent cough develops which occurs in explosive bursts, sometimes ending with a high-pitched whoop and vomiting. Between bursts of coughing the child appears well. Coughing attacks continue to occur for 4 to 6 weeks and are more common at night. The bacterium is spread from person to person by droplets that are expelled during sneezing and coughing. The incubation period, the time between when a person is exposed until symptoms develop, is 7 to 10 days.