<prompt> Main period of communicability of whooping cough?Incubation periodParoxysmal stageCatarrhal stageConvalescent stage  <response>: Ans. is c i.e.,Catarrhal stage Peussis, also called 100 day cough, is caused by Bordetella peussis only 5 cases are caused by B. parapeussis.there is no cross immunity between B. peussis and B. parapeussis.Period of infectivity communicability extends from a week after exposuse to about 3 weeks after the onset of paroxysmal stage. Catarrhal stage is most infective. Secondary attack rate is high, i.e. 90. 