Pertussis is the medical name for whooping cough, a serious bacterial infection of the lungs and breathing passages. The disease gets its common name from its most recognizable symptom: violent coughing fits followed by a desperate, gasping breath that makes a high-pitched whoop sound.

Pertussis causes intense, uncontrollable coughing that can last for weeks or even months. Before vaccines were developed in the 1940s, pertussis killed thousands of children every year in the United States alone.

Today, babies receive the pertussis vaccine (usually combined with vaccines for diphtheria and tetanus, called DTaP) to protect them from this dangerous disease. The vaccine is one of modern medicine's great success stories, though pertussis hasn't disappeared completely. Doctors and scientists still use the medical term pertussis in research, vaccination records, and when discussing outbreaks. When you hear someone mention their “DTaP shot,” that P stands for pertussis.