Most common source of infection for whooping cough ?

Ans. is `c' i.e., Case Peussis is a respiratory tract infection caused mainly by B. peussis. Source of infection A case of peussis (not carrier). There is no subclinical case and chronic carrier state does not exist. Infective period whooping cough is most infectious during catarrhal stage. The infective period extend from a week after exposure to about 3 weeks after the onset of the paroxysmal stage. Secondary attack rate -4 It is high, i.e. 90%. Age group - It is a disease of infants and young children (< 5 years of age). Mean age of infection is between 2 0- 3 0 months.