Laboratory, epidemiological and clinical characteristics of pertussis in children and close contacts: a cross-sectional study.

Purpose: To investigate the epidemiological and clinical characteristics of pertussis in children and close contacts.

Methods: Nasopharyngeal swabs and blood samples of clinically suspected children with pertussis and their close contacts from 2018 to 2022 were collected for pathogen detection of Bordetella pertussis. Questionnaires were designed to investigate the basic information and infection status of pertussis children cases and their close contacts. Descriptive epidemiological analysis was performed on the results.

Results: 1229 confirmed children cases of pertussis were collected and infants < 1 year old were the most affected (77.7%). Etiological data were collected from 587 close contacts of 269 confirmed cases and the infection rate was high (24.4%). The positive detection rate of parents, especially mothers, was significantly higher than that of other groups (32.2% vs. 18.4%, P < 0.001); The rates of misdiagnosis or missed diagnosis in pertussis children (92.2%) and close contacts (99.8%) were very high, and the distribution of symptoms between pertussis children and their close contacts was different (χ² = 535.328, P < 0.001); The vast majority of pertussis children (84.0%) were diagnosed with upper respiratory tract infection or trachea/bronchitis while 91.0% of close contacts did not seek medical attention (χ² = 685.373, P < 0.001).

Conclusion: Infants < 1 year old are at high risk in pertussis. Pertussis infection in close contacts of confirmed children is underestimated. Caregivers who are positive for pertussis but missed or misdiagnosed seriously may be a main source of pertussis infections in children. Adjusting the current pertussis immunization strategy in China is necessary.