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Pertussis (Whooping Cough)

An acute, highly communicable bacterial disease, characterized by a paroxysmal or spasmodic cough that usually ends in a prolonged, high-pitched, crowing inspiration (the whoop).

Etiology and Epidemiology
The causative agent is Bordetella pertussis. B.parapertussis closely resembles this organism; it causes parapertussis, which may be clinically indistinguishable from pertussis but is usually milder and less often fatal.

Transmission is by aspiration of B.pertussis sprayed into the air by a patient, particularly in the catarrhal and early paroxysmal stages. Transmissions by contact with contaminated articles is rare.

Pertussis is endemic throughout the world. One attack does not confer natural immunity for life, but second attacks, if they occur, are usually mild and often unrecognized.

Symptoms and Signs
The incubation period averages 7 to 14 days. The disease lasts about 6 wk and consists of 3 stages: catarrhal, paroxysmal and convalescent. The catarrhal stage begins insidiously, generally with sneezing, lacrimation, or other signs of coryza; anorexia; listlessness; and a troublesome, hacking nocturnal cough that gradually becomes diurnal. Fever is rare.

The cough becomes paroxysmal after 10 to 14 days. There are 5 to > 15 rapidly consecutive coughs followed by the whoop, a hurried, deep inspiration. After a few normal breaths, another paroxysm may being. Vomiting subsequent to paroxysms or due to gagging on the tenacious mucus is characteristic. In infants, choking spells (with or without cyanosis) may be more common than whoops.

The convalescent stage usually begins within 4 wk; paroxysms are not so frequent or severe, vomiting decreases, and the patient looks and feels better. The average duration of illness is about 7wk. Paroxysmal coughing may recur for months, usually induced by irritation from a URI.

Diagnosis
The catarrhal stage is often difficult to distinguish from bronchitis or influenza. Cultures of nasopharyngeal specimens are positive for B.pertussis in 80 to 90% of cases in the catarrhal and early paroxysmal stages. Specific fluorescent antibody testing of pasopharyngeal smears accurately diagnosis pertussis but is not as sensitive as culture. Parapertussis is differentiated by culture of the fluorescent antibody technique.

Prognosis and Complications
Pertussis is serious in children under age 2. The disease is troublesome but rarely serious in older children and adults, except in the aged.

The most frequent complications are respiratory, including asphyxia in infants. Bronchopneumonia is also a frequent complication in the aged and may be fatal at any age. Interstitial and subcutaneous emphysema and pneumothorax are infrequent consequences of the increased intrathoracic pressure during paroxysms. Bronchiectasis, particularly in debilitated children, and residual emphysema can result. Convulsions are common in infants but rare in older children. Hemorrhag into the brain, eyes, skin and mucous membranes can result from severe paroxysms and consequent anoxia. Otitis media is frequent.

Prophylaxis
Active immunization is given routinely to most children combined with diphtheria, tetanus and polio regime. Passive immunization is unreliable and is not recommended.

Treatment
Hospitalization is recommended for seriously ill infants because expert nursing care is important. Bed rest is unnecessary for older children with mild disease.

Seriously ill infants should be kept in a darkened, quiet room and disturbed as little as possible, since any disturbance can precipitate serious paroxysmal spells with anoxia.

Antibiotics should be used only for bacterial complications such as bronchopneumonia and otitis media.

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