Outbreak Investigation of Hand, Foot, and Mouth Disease in a Kindergarten School in Phiman Sub-district, Mueang Satun District, Satun Province, during 15 August–4 September 2025

Abstract

Background: On August 14, 2025, the Surveillance Unit of Satun Hospital identified a cluster of Hand, Foot, and Mouth Disease (HFMD), three students from one municipal kindergarten presented with fever, oral ulcers, and palm/sole rashes. An investigation was conducted from August 15 to September 4, 2025, to confirm the outbreak, characterize its distribution, identify risk factors, and implement control measures.

Methods: A descriptive epidemiological study was conducted through medical record reviews at Satun Hospital and active case finding via interviews with teachers and parents. A clinical case was defined as a student meeting at least two of the following five criteria: 1) multiple oral ulcers, 2) vesicular or maculopapular rash on palms, 3) vesicular or maculopapular rash on soles, 4) fever (> 37.5°C), or 5) clinical features of herpangina. Laboratory confirmation was performed via RT-PCR of throat swabs for Enterovirus, alongside an environmental risk assessment. Finally, a 1:2 Case-Control study was conducted in a Satun kindergarten to identify risk factors, comparing cases with asymptomatic controls. Data was analyzed using Odds Ratios (OR) and 95% Confidence Intervals (CI).

Results: An HFMD outbreak was identified at a Satun kindergarten from July to August 19, 2025. Of 23 cases (3.44% attack rate), 1 was confirmed (EV71), 1 probable, and 21 suspected, with no fatalities. The highest classroom-specific attack rate was 37.50% in kindergarten 2/4. A retrospective case-control study found significant risk factors: sharing utensils/bottles (OR = 4.97, 95% CI = 1.87–13.20) and contact with ill neighbors (OR = 4.69, 95% CI = 1.60–13.74). These correlated with environmental findings, including communal bedding storage, shared toys, and improper disinfection, which facilitated rapid transmission among students.

Conclusion: This propagated HFMD outbreak was caused by Enterovirus 71. Transmission was primarily driven by the sharing of personal utensils and inadequate environmental sanitation. Implementation of control measures—including active screening, a 5-day classroom closure, and standardized disinfection—effectively terminated the outbreak. The final case was reported on August 19, 2025.