Pertussis occurs worldwide. Pertussis bacteria live in the mouth, nose, and throat of an infected person. Pertussis spreads easily from person to person. People get pertussis by breathing in droplets expelled from the nose or throat of an infected person during coughing or sneezing. It is also spread by direct contact with discharges from the nose or throat of an infected person.
Pertussis begins as a mild upper respiratory infection.
The first symptoms are like those of a cold, including sneezing, runny nose, low-grade fever, and a mild cough. Within 2 weeks, the cough becomes much worse. The violent coughing spells are worse at night and can last for as long as 1 to 2 months. The spells can make it hard for a child to eat, drink, or even breathe. Infants under age 6 months, adolescents, and adults generally have milder symptoms without the typical whoop.