Whooping cough (pertussis) is a highly contagious bacterial infection (Bordetella pertussis or B. parapertussis bacteria) of the upper respiratory system, specifically the area where the nasal passages meet the back of the throat (nasopharynx). The infection causes irritated airways and severe coughing spells that often lead to a characteristically loud whooping or crowing sound as air is inhaled.

Symptoms can occur in three distinct stages that altogether may last 6 to 10 weeks or longer. The first stage is coldlike symptoms, including sneezing, runny nose, and mild coughing. The second stage is a dry, hacking cough that changes to bursts of uncontrollable, often violent coughing. The third stage is a cough that sounds worse. Severe coughing spells may cause vomiting, exhaustion, and a blue tint to the skin and nail beds.

Although whooping cough can occur at any age, it is of greatest concern in children younger than 4 months and adults ages 60 or older, because their risk of complications is higher than that of other people. The disease may be prevented or controlled if a child gets periodic immunizations with the pertussis vaccine between 2 months and 6 years of age. But the protection provided by the vaccine wears off over time. A booster shot is recommended for adolescents and adults.

Taking antibiotics early in the illness may help shorten the illness or prevent it from progressing to the stage in which severe coughing spells occur. Babies with whooping cough may need hospitalization, especially when they are younger than 4 months of age.

Complications include infection (such as pneumonia) or problems related to the straining during coughing spells, such as a hernia. In rare cases, whooping cough can cause death.