Symptoms
The symptoms of pertussis typically develop within 5 to 10 days after exposure to the bacterium. The early symptoms of pertussis are similar to those of a common cold, including runny nose, low-grade fever, and mild cough. However, as the disease progresses, the cough becomes more severe and can last for several weeks or even months. The characteristic symptom of pertussis is a coughing fit that ends with a loud "whoop" sound as the person tries to inhale air. Infants and young children may also experience vomiting after coughing spells and may turn blue due to lack of oxygen.
Causes
Pertussis is caused by the bacterium Bordetella pertussis, which infects the respiratory tract and produces toxins that damage the lining of the airways. The bacteria are spread through respiratory droplets when an infected person talks, coughs, or sneezes. Pertussis is most contagious during the early stages of the disease, when symptoms are mild and may be mistaken for a cold. However, the bacteria can remain in the respiratory secretions for several weeks, even after the symptoms have resolved, and can still be transmitted to others.