Outbreak of Influenza a at the Refuge Center after the East Japan Great Earthquake Disaster

An outbreak of influenza a occurred at the Tatekoshi Elementary School refuge center in Natori City, Miyagi Prefecture after the East Japan great earthquake disaster of March 11, 2011. Two hundred evacuees were housed at the refuge center of whom 40% were elderly people 65 years and older. Five days after the initial case on April 8, intervention was requested to deal with the influenza outbreak by the Chairperson of the Natori City Medical Association which was providing medical services at the refuge center. On April 8, we arrived to implement intervention measures, when non-pharmaceutical intervention (NPI) through the isolation of all individuals with early onset of influenza had been already been carried out. However, except for isolation, NPI including hand hygiene was not adequate. On the other hand, antiviral prophylaxis had been administered to 22 evacuees. Therefore, we focused on reinforcement of basic NPI measures including site staff education; improvement of the face mask wearing rate; emphasizing the importance of hand hygiene; implementation of adequate ventilation; aggressive detection of symptomatic individuals and monitoring family members for onset of symptoms; and isolation of persons at onset of infection. On the other hand, we also emphasized to the site physicians that antiviral prophylaxis was only effective if basic NPI measures were strictly enforced and that prophylaxis should only be considered if the outbreak expanded. On April 13, we made a second intervention visit. The last new case occurred on April 14. Influenza outbreak at a refuge center has not been previous reported and no guidelines have been established. Our experience suggests that prophylaxis should only be used to supplement NPI measures, which should be strengthened as the main intervention strategy, and should only be considered based on the extent of outbreak and patient risk factors.