Pertussis (whooping cough) is a highly contagious disease of the respiratory tract caused by Bordetella pertussis bacteria.
Pertussis is transmitted from infected to susceptible individuals by droplets through coughing or sneezing or when in close proximity i.e. sharing breathing space. The B. pertussis bacteria in the droplets attach to the cilia that line part of the upper respiratory system. Subsequently they release toxins, which damage the cilia and cause airways to swell.
The incubation period is approximately 7 to 10 days, with an insidious onset and initial symptoms indistinguishable from a minor upper respiratory infection (the catarrhal stage). Fever is usually minimal throughout the course of infection. The cough, initially intermittent, progresses within 1 or 2 weeks to become paroxysmal. The paroxysms increase in both frequency and severity, and then gradually subside over a period of 2 to 6 weeks, but sometimes much longer (so-called hundred day cough) [1-3]. During the paroxysmal stage, a series of rapid coughs without intervening inspiration will often be followed by the characteristic whoop. During a paroxysm, cyanosis may occur and vomiting may follow . In young infants, the paroxysms may also be followed by periods of apnea. Pneumonia is a relatively common complication; seizures and encephalopathy occur more rarely. Untreated patients may be contagious for three weeks or more following onset of the cough .
Pertussis can affect all age groups, however it is most dangerous for infants, who account for nearly all pertussis hospitalizations and deaths. Pertussis in older children, adolescents and adults is most often unrecognized because its clinical course is often atypical . Newborns who get pertussis are often infected by older siblings, parents, or caregivers who might not even know they have the disease.