Abstract: Objective To analyze the epidemiological characteristics, transmission dynamics, and effectiveness of control measures of a hand, foot, and mouth disease (HFMD) outbreak at Z Primary School in Futian District, Shenzhen, to provide a scientific basis for the management of school-based outbreaks. Methods Field epidemiology, RT-PCR etiological testing, a retrospective cohort study, and transmission dynamics analysis were employed. Case finding, individual interviews, and investigation of risk factors were conducted among all students, faculty, and patients' families at Z school. The R₀ and R_t were calculated. Results A total of 24 cases were identified (18 students from Z school and 6 from other schools). The morbidity rate in the affected classes at Z school was 6.41% (18/281). The etiological investigation identified Coxsackievirus A16 (CVA16) and other enteroviruses as the primary pathogens. The outbreak comprised six generations of transmission, with close contact among friends (56.17%) and within families (37.50%) as the main transmission routes. The secondary attack rate within families was 88.89%, leading to cross-class and cross-school transmission. Close contact with an HFMD patient within 10 days prior to onset was a significant risk factor for transmission (RR=13.33, 95% CI 1.81-98.04). The classroom attack rate increased significantly with a longer interval from symptom onset to isolation (P<0.01). Following the implementation of case isolation and class suspension, the reproduction number decreased from an R₀ of 2 to an R_t of 0 (P=0.01). Conclusion This was an HFMD outbreak in a primary school caused by CVA16 and other enteroviruses. Insufficient school medical personnel and underreporting of cases were significant factors in the delayed detection of the outbreak. Close contact within families and among friends should be emphasized as a key factor in the spread of the epidemic. Shortening the time from onset to isolation, strengthening home-school collaboration and prevention, increasing the number of school medical staff, and enhancing symptom surveillance are critical measures for the early interruption of outbreaks.

Key words: Hand, foot, and mouth disease, Outbreak, Students, Epidemiological investigation