Objective. To study the clinical presentation of culture-confirmed pertussis in children and their contacts with cough illnesses in an outpatient setting.

Methodology. In conjunction with a large pertussis vaccine efficacy trial in Germany, a central laboratory to isolateBordetella species from nasopharyngeal specimens was established in Erlangen in October 1990. Pediatricians in private practices in southern Germany, the Saar region, and Berlin were encouraged to obtain nasopharyngeal specimens and clinical characteristics from patients with cough illnesses ≥7 days' duration.Bordetella species were isolated by use of calcium alginate swabs, Regan–Lowe agar, and modified Stainer–Scholte broth. Clinical characteristics were determined by initial and follow-up questionnaires.

Results. From October 1990 to September 1996, 20 972 specimens were submitted, and B pertussis was isolated in 2592 instances (12.4%). Of the culture-proven cases, 50.7% were female, and the age range was 6 days to 41 years, with a mean and median of 4.3 years and 4.1 years, respectively. The following characteristics were noted. Only 4% of the patients had received pertussis vaccine. Of unvaccinated patients, 90.2% had paroxysmal cough, 78.9% demonstrated whooping, and 53.3% presented with posttussive vomiting; 5.7% had fever ≥38°C. The duration of cough was ≤4 weeks in 37.9% and ≤3 weeks in 17.4%. Leukocytosis and lymphocytosis (values above the age-specific mean) were observed in 71.9% and 75.9% of unvaccinated patients, respectively. The overall complication rate was 5.8%, and pneumonia (29%) was the most frequent complication. In infants <6 months of age, the rate of complications was 23.8%. One death in a 7-month-old infant occurred.

Conclusions. Typical symptoms of pertussis were observed in the great majority of patients regardless of age group. However, the duration of cough was surprisingly short in one sixth of the patients. These short illness cases would not be classified as pertussis according to the World Health Organization clinical case definition, which requires ≥21 days of spasmodic cough.

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