[Report on the Epidemic Investigation of the Pertussis Outbreak in Gyeongsangnam-do, 2023-2024]

Pertussis is a legally designated Class 2 infectious disease managed through the national vaccination program. While the number of patients in the Republic of Korea has decreased significantly due to increased vaccination rates, caution is still necessary because the disease affects various age groups, from unvaccinated children to adolescents and adults. From October 1, 2023, to February 29, 2024, 268 pertussis cases were reported in the Gyeongsangnam-do area, which has experienced two small-scale outbreaks in the past 10 years. To explore effective infectious disease management strategies, recent outbreak cases were analyzed, and the field response process was described. An analysis of 268 pertussis cases showed that the majority (87.2%) of confirmed cases occurred in Changwon-si Masanhoewon-gu and Haman-gun in Gyeongsangnam-do, primarily among school-aged children aged 5-14 years (89.9%). Among the patients, 258 (96.3%) showed symptoms of coughing, 60 (22.4%) required hospitalization, and the rest recovered through outpatient treatment. The main route of infection was identified as transmission through group living environments in educational facilities, such as daycare centers, schools, academies, and after-school classes. The decrease in immunity among school-aged children after initial vaccinations in infancy was identified as a major factor in the spread of the outbreak. Hence, it is necessary to develop vaccination strategies tailored to the specific characteristics of areas affected by the epidemic and to actively promote clinical and epidemiological education within the community providing information about pertussis.