Pertussis should be suspected in a child who has severe paroxysmal coughing with posttussive emesis that occurs after mild symptoms of an upper respiratory tract infection. Pertussis occurs in three phases. The first phase is a catarrhal stage that is characterized by mild upper respiratory tract infection symptoms of nasal congestion, rhinorrhea, conjunctival injection, and low-grade fever. The second phase is the paroxysmal stage, which occurs between 2 and 4 weeks of illness and is characterized by increasingly frequent and severe coughing paroxysms with posttussive emesis. Subconjunctival hemorrhage may occur due to the severity of the coughing spells. The classic whoop sound, which may or may not be present, occurs from the deep inspiratory effort after a coughing paroxysm. The third phase is the convalescent stage, which usually lasts 1 to 2 weeks and is associated with slowly improving cough. However, in some patients the cough may persist for weeks to months. The total duration of classic pertussis usually is 6 to 8 weeks, although symptoms may only last 3 weeks. Complications of pertussis include seizures, pneumonia, encephalopathy, and rarely death.

Pertussis is caused by Bordetella pertussis, a fastidious, gram-negative, pleomorphic bacillus. Humans are the only known hosts of B pertussis. Transmission occurs via close contact with respiratory tract secretions of infected patients. Almost 50% of the cases are reported in adolescents and adults, but 24% of cases in the United States occur in infants younger than 6 months of age and 43% in children younger than 5 years of age. Patients are most contagious during the catarrhal stage before the onset of coughing paroxysms.

Culture of B pertussis is the diagnostic test of choice and requires inoculation of nasopharyngeal mucus onto special medium with incubation for 10 to 14 days. A positive culture is diagnostic, but cultures may be negative late in the course of disease. A direct immunofluorescent assay of nasopharyngeal secretions for pertussis is available, but it has variable sensitivity and low specificity, suggesting the need for culture confirmation in all suspected cases. No single serologic test is diagnostic of pertussis. (Addendum, Pertussis PCR is now the diagnostic test of choice - JS)

Antibiotics provided in the catarrhal stage limit disease duration, but have no effect on disease once the paroxysmal stage has begun. However, antibiotics are recommended to limit the spread of disease. The drug of choice for treatment of pertussis is oral erythromycin 40 to 50 mg/kg per day qid for 14 days. Azithromycin and clarithromycin may be effective in shorter courses of 5 to 7 days. Supportive management is necessary in some patients.

Pertussis immunization is recommended for routine prevention of the infection. The acellular vaccine usually is administered in  combination with diphtheria and tetanus toxoid. Incompletei mmunization and failure to provide repeated booster vaccination can lead to an increased risk of disease. Complications of immunizations include local and febrile reactions, allergic reactions, seizures, and other rare problems.

An aspirated foreign body may cause a cough and is most common in children 9 months to 2 years of age. Usually there is a history of foreign body aspiration. Asymmetric breath sounds may indicate a foreign body. Persistent paroxysmal coughing is not typical, and a prodrome of nasal congestion and rhinorrhea followed by paroxysmal coughing suggests an infectious etiology. Viral illnesses typically are associated with cough, but not with severe paroxysms and deep whooping. Gastroesophageal reflux may cause chronic cough in some individuals, but intermittent spasms and nighttime cough are more typical than paroxysmal coughing. Finally, allergic rhinitis can be  associated with nasal congestion, rhinorrhea, wheezing, and cough, but paroxysmal coughing is unusual.

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