Pertussis, or whooping cough, is a highly contagious disease involving the respiratory tract. It is caused by bacteria called Bordetella pertussis that is found in the mouth, nose, and throat of an infected person. Pertussis can occur at any age, but severe illness is more common in young children who have not been immunized, and infants suffer the highest rates of hospital admission and death. Pertussis is usually transmitted from one person to another when infected people cough or sneeze, spreading droplets that contain the Bordetella pertussis bacteria. Older siblings or adults who may be carrying the bacteria in their nose and throat can infect an infant.
Pertussis begins as a mild respiratory infection.
Symptoms resemble those of a common cold, including sneezing, runny nose, a low-grade fever, and mild cough. Within two weeks the cough becomes more severe and is characterized by episodes of prolonged and uncontrollable coughing ending in a high pitched whooping sound from sucking in air. Coughing spells can become so bad that it is hard for infants to eat, drink, or breathe. A thick, clear mucus may be discharged. These episodes may persist for two weeks or more, and are more frequent at night.