Survey of pertussis in patients with prolonged cough

Pertussis is an acute respiratory tract illness resulting from Bordetella pertussis. Widespread use of pertussis vaccine over the past 50 years has decreased the incidence of pertussis. The incidence of pertussis in adolescents and adults has increased in many areas of the world. This study aimed to evaluate the etiologic role of B. pertussis in patients with prolonged cough in Taiwan. Patients with cough lasting for more than 1 week were recruited. Nasopharyngeal swabs were taken for culture of B. pertussis and detection of nucleic acid of B. pertussis by polymerase chain reaction. Serum samples were collected in a subset of patients for assay of immunoglobulin G and immunoglobulin A antibodies against pertussis toxin. In total, 111 patients were recruited. Thirty-three patients agreed to have their serum samples taken and tested. Eight patients had evidence of acute infection with B. pertussis; among them, 1 was diagnosed by polymerase chain reaction and 7 by serology. Older subjects were more likely to suffer from pertussis than younger subjects. The incidence of pertussis in patients with prolonged cough was 7.2%. However, the rate could have been as high as 21% in those with serum samples tested. We conclude that pertussis is a prevalent disease in Taiwan, especially in adolescents and adults.