Outbreak investigation of influenza A in a prison in Sawankhalok district, Sukhothai province, Thailand, September 2022

Abstract

                The Office of Disease Prevention and Control 2 region was notified of a cluster of suspected influenza cases in prison on September 13, 2022. An investigation was conducted to describe magnitude and distribution of the outbreak, to identify risk factors, and to determine appropriate control measures. We generated the case definition of suspected and confirmed influenza cases and conducted active case finding by interviewing  officers and prisoners who got sick between 1 – 14 September 2022 about their symptoms and risk factors. Then, we collected throat and/or nasopharyngeal swab from 10% of cases and tested with real time RT-PCR method. An environmental study was also conducted. A total of 80 case met our case definition (attack rate = 12.1%), 79 prisoners (99.7%) and 1 officer (1.3%). The morbidity rate for male inmates was 12.8 and female 17.6. All of them were not severe or dead. Laboratory investigation detected Influenza A H3Nx in 7 out of 9 samples. Formerly, prisons provided inclusive training for male and female inmates. As a result of the investigation, control measures has been set up by isolating sleeping areas of suspected cases and recommend encouraging everyone to wear a mask, wash hands frequently, and do not share personal items. Furthermore, we emphasized on avoiding social events during the epidemic period while improving screening before holding social events in the normal period.