An outbreak investigation of influenza A (H3NX) in a prison in Phetchabun province

Abstract

     On February 24, 2023, the Social Medicine Department at Phetchabun Hospital was notified of an influenza outbreak in a prison, with 98 cases reported. Most patients presented with fever, cough, sore throat, headache, and muscle pain, while some also experienced fatigue and loss of appetite. The Surveillance and Rapid Response Team conducted an investigation from February 24-26, 2023, aiming to confirm diagnosis and outbreak, describe its epidemiological characteristics, and implement control measures. This descriptive cross-sectional study, conducted from February 1 to March 31, 2023, included inmates and staff. Data were collected through medical record reviews and active case finding using a questionnaire. Suspected cases were defined by the presence of fever and cough, along with symptoms such as sore throat, runny nose, body aches, or fatigue. Probable cases were those who tested positive for influenza using Rapid Influenza Diagnosis Tests, while confirmed cases were identified through RT-PCR. Environmental assessments of the prison were also conducted. The study identified 624 cases, all inmates, with a male-to-female ratio of 11:1. The median age was 34 years. Common symptoms included sore throat (95.95%), headache (94.34%), and runny nose (91.26%). Laboratory tests confirmed the presence of Influenza A (H3NX). In conclusion, this outbreak was Influenza A (H3NX) outbreak and was characterized by a rapid increase in cases, which significantly decreased following detection and investigation. The outbreak was likely caused by the introduction of the virus into the overcrowded prison environment, facilitating rapid transmission.