The whooping cough bacteria are spread from person to person in airborne droplets or by direct contact with infected throat or nasal discharges. Coughing and sneezing are the most common modes of transmission.
Once infection with the whooping cough bacteria has occurred, the time until symptoms appear (incubation period) is usually between five to 10 days, though it can be as long as 21 days.
The contagious period is from seven days following infection with the whooping cough bacteria, to up to one month after the appearance of the coughing spasms, with the most contagious period being during the catarrhal stage.
If there is an outbreak of whooping cough it is advisable to keep uninfected children (especially those who are unimmunised) away from the source of the infection until after the contagious period has passed. Likewise, children with whooping cough should be removed from school or daycare until they are no longer infectious.