Pertussis, or whooping cough, is a contagious disease that can cause a prolonged and sometimes severe cough illness. It is caused by the bacterium, Bordetella pertussis, and is found in the nose and throat of an infected person. An infected person has cough episodes that may end in vomiting or cause a "whoop" sound when the person breathes in air. Pertussis can occur at any age but severe illness is more common in infants and young children who have not been immunized.
The appearance of symptoms is usually 7 to 10 days after exposure. If a person is exposed to pertussis, certain antibiotics may help prevent or lessen the disease. Pertussis can be prevented in children by immunizing them in early infancy. Vaccine-induced immunity wanes among older children. Pertussis vaccine is given at 2, 4, 6, and 15 months of age, and again when a child enters school. At least 3 doses are necessary to protect a child from pertussis.