Adult pertussis is unrecognized public health problem in Thailand

Nirada Siriyakorn, Pornvimol Leethong, Terapong Tantawichien, Saowalak Sripakdee, Anusak Kerdsin, Surang Dejsirilert, Leilani Paitoonpong

Although pertussis has been considered a disease of childhood, it is also recognized as an important respiratory tract infection in adolescents and adults. However, in countries with routine vaccination against pertussis with high coverage, pertussis is not usually taken into consideration for the etiology of prolonged cough in adults. Previous studies in a variety of populations in developed countries have documented that pertussis is quite common, ranging from 2.9 to 32 % of adolescents and adults with prolonged cough. The anticipation and early recognition of this change in the epidemiology is important because the affected adolescents and adults act as reservoirs of the disease and source of infection to the vulnerable population of infants, for whom the disease can be life threatening. We conducted a prospective study to determine the prevalence of pertussis in Thai adults with prolonged cough. Seventy-six adult patients with a cough lasting for more than 2 weeks (range, 14-180 days) were included in the present study. The data regarding medical history and physical examination were carefully analyzed. Nasopharyngeal swabs from all patients were obtained for the detection of deoxyribonucleic acid of Bordetella pertussis by the polymerase chain reaction (PCR) method. Paired serum samples were collected and tested for IgG antibody against pertussis toxin by using an ELISA method. Of 76 adult patients, 14 patients (18.4 %) with the mean age of 59 (range, 28-85) years and the mean duration of cough of 34 (range, 14-120) days had laboratory evidence of acute pertussis infection. One patient was diagnosed by the PCR method, while the rest had serological diagnosis. Whooping cough is a significantly associated symptom of patients with chronic cough who had laboratory evidence of pertussis. (p < .05, odds ratio 3.75, 95 % confidence interval: 1.00,14.06) CONCLUSION: Pertussis is being increasingly recognized as a cause of prolonged, distressing cough among adults in Thailand. This result addresses the need of pertussis vaccination in Thai adults for preventing transmission to a high risk group such as newborn infants.