Pertussis is a contagious disease caused by a bacterium.
It causes severe spells of coughing which can interfere with eating, drinking, and breathing. Some people who recover from pertussis may suffer from mental retardation. Pertussis can occur in all ages but is most common in children younger than 5 years, especially infants less than 1 year of age. Pertussis is spread through the air after an infected person coughs or sneezes. Other people then breathe in infected droplets.