Pertussis or whooping cough is a highly contagious disease of the respiratory tract caused by Bortedella pertussis that kills close to 300,000 people every year. It is transmitted by direct contact with airborne discharges from infected persons. Children are routinely immunized against pertussis. The pertussis vaccine is usually combined with vaccines for diphtheria and tetanus such as the DTP (diphtheria-tetanus-pertussis) vaccine.