Pertussis is an acute infection of the respiratory tract caused by Bordetella pertussis. The "violent cough" is the most consistent and prominent feature of the illness. The inspiratory sound made at the end of an episode of paroxysmal coughing gives rise to the common name for the illness, "whooping cough"; however, this feature is variable, being uncommon in infants less than 6 months of age and frequently absent in older children and adults.
The incubation period is 7 days.
The clinical course passes through 2 phases:
1. Catarrhal phase: which is indistinguishable from the common cold.
2 Paroxysmal phase: the cough becomes more frequent and spasmodic with repetitive bursts of 5 to 10 coughs, often within a single expiration. Posttussive vomiting is frequent, with a mucous plug occasionally expelled at the end of an episode. The episode may be terminated by an audible whoop, which occurs upon rapid inspiration against a closed glottis at the end of a paroxysm.
In some cases the case does not present with the classical manifestations and in this setting is not any different from any respiratory tract infection.
If the disease presents with the classical manifestations outlined above, then diagnosis is made rather easily based on the clinical findings. Culture of nasopharyngeal secretions remains the "gold standard" of diagnosis.
Marked lymphocytosis is seen in the blood picture (due to the effects of lymphocyte promoting factor).
The catarrhal stage should be treated with erythromycin, the idea being to eradicate the organism while still in the nasopharynx. Supportive care may be required during the paroxysmal phase.
The mainstay of pertussis prevention is active immunization with pertussis vaccine.
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