Detection of Bordetella spp. in children with pertussis-like illness from 2018 to 2024 in China.

OBJECTIVE

To evaluate the role of Bordetella pertussis (B. pertussis), B. parapertussis, B. holmesii, and B. bronchiseptica on pertussis resurgence in China, particularly the sharp rise since the latest winter.

METHODS

Nasopharyngeal swabs collected from children with pertussis-like illness from January 2018 to March 2024 were cultured to detect B. pertussis, B. parapertussis, B. holmesii, and B. bronchiseptica, and tested for all of these except for B. bronchiseptica using a pooled real-time polymerase chain reaction (PCR) kit targeting insertion sequences ptxS1, IS481, IS1001, and hIS1001.

RESULTS

Out of the collected 7732 nasopharyngeal swabs, 1531 cases tested positive for B. pertussis (19.8%, 1531/7732), and 10 cases were positive for B. parapertussis (0.1%, 10/7732). B. holmesii and B.bronchiseptica were not detected. The number of specimens and the detection rate of B. pertussis were 1709 and 26.9% (459/1709) in 2018, 1936 and 20.7% (400/1936) in 2019, which sharply declined to 308 and 11.4% (35/308) in 2020, 306 and 4.2% (13/306) in 2021, and then notably increased to 754 and 17.6% (133/754) in 2022, 1842 and 16.0% (295/1842) in 2023, 877 and 22.3% (196/877) in the first quarter of 2024. The proportion of children aged 3 to less than 6 years (preschool age) and 6 to 16 years (school age) in pertussis cases increased significantly during the study period, especially the proportion of school-aged children increased from 2.0% (9/459) in 2018 to 40.8% (80/196) in 2024.

CONCLUSIONS

B. pertussis was the predominant pathogen among children with pertussis-like illness in China, with sporadic detection of B. parapertussis and no detection of B. holmesii or B.bronchiseptica. The preschool and school-age children are increasingly prevalent in B. pertussis infection cases, which may be associated with the latest rapid escalation of pertussis outbreak.