Whooping cough or pertussis is a contagious disease of the upper respiratory tract caused by the bacterium Bordetella pertussis. Whooping cough is transmitted via droplets in the air from sneezing or coughing and individuals are considered infectious from just before and up to 21 days after the onset of the cough. Usually it has an incubation period of seven to ten days, and the disease lasts six to eight weeks.