Influenza B Virus Outbreak At A Religious Residential School For Boys In Northern Bangladesh, 2011

Background: National media reported a febrile illness among dormitory residents of a boys' religious school. We investigated the outbreak to identify cause.Methods: Individuals with fever (>100 degrees F) and cough or sore throat between 1 and 13 August 2011 were influenza-like-illness (ILI) case-patients. We collected histories and specimens from hospitalized case-patients and visited campus to explore environmental context.Results: All 28 case-patients were dormitory residents including 27 hospitalizations. Accommodation space per resident was <0.8 square metres. Nasal and oropharyngeal swabs from 22 case-patients were positive for influenza B virus using real-time reverse transcription polymerase chain reaction (rRT-PCR).Conclusions: Overcrowding likely facilitated transmission leading to this dormitory outbreak.