Investigation of influenza A (H3) outbreak in a scout camp Pathumrat District, Roi Et Province, Thailand, February 2023

Abstract

An outbreak investigation of Influenza A (H3) in a scout camp in Pathumrat district, Roi Et province, February 2023, aimed to confirm the diagnosis of the outbreak, identify the causes or risk factors associated with the outbreak, and determine control and prevention measures. The study employed a descriptive and analytical epidemiological approach, utilizing a retrospective cohort study design. An active case finding was conducted using a case investigation form. Based on a case definition that refers to students or teachers exhibiting at least two symptoms (fever, cough, sore throat, runny nose, headache, muscle aches) from February 1 to February 13, 2023, the additional cases were identified and the environmental investigation were conducted. Throat swabs were collected for laboratory confirmation. From a total of 247 students and teachers, 163 cases met the case definition, resulting in an attack rate of 65.99%. There were 7 confirmed cases of Influenza A (H3) out of 7 samples tested, and 156 were suspected cases. The attack rate, by gender, 76.29% in male and 53.57% in female. The minimum age was 9 years and the maximum age was 60 years (median age of 13 years). The rate of illness was classified by age group: 5-9 years old (100%), 10-14 years (73.67%), 15-19 years (60.00%), 20-24 years (0%), and 25 years or older (27.27%). The most common symptoms were cough (88.34%), runny nose (73.01%), fever (64.42%), sore throat (55.21%), and headache (46.01%). No severe cases or deaths were reported. Sharing drinking glasses with others was identified as a significant risk factor for the outbreak (AOR=3.32, 95% CI=1.47-7.50). Wearing a mask was found to be a protective factor (AOR=0.46, 95% CI=0.26-0.80). The outbreak was cause by influenza A (H3). Effective control measures and public health education regarding influenza were implemented which included stop sharing things with others, wearing a mask, screening and isolating symptomatic students, and allowing sick students to stay home. Therefore, the outbreak was effectively controlled and contained.