The usual incubation period for pertusis is -

Ans. is 'a' i.e., 7-14 days The incubation period of pertussis is usually 7-14 days, but not more than 3 weeks.More question on PertussisMost infectious during catarrhal stage.Infective period extends from a week after exposure to about 3 weeks after the onset of paroxysmal stage.The source of infection is a case of pertussis.There is no evidence that infection is ever subclinical a chronic carrier state does not exist.Secondary attack rate is 90% in unimmunized household contacts.