Abstract

BackgroundThe Great East Japan Earthquake of magnitude 9.0 that struck on 11 March 2011 resulted in more than 18000 deaths or cases of missing persons. The large-scale tsunami that followed the earthquake devastated many coastal areas of the Tohoku region, including Miyagi Prefecture, and many residents of the tsunami-affected areas were compelled to reside in evacuation centres (ECs). In Japan, seasonal influenza epidemics usually occur between December and March. At the time of the Great East Japan Earthquake on 11 March 2011, influenza A (H3N2) was still circulating and there was a heightened concern regarding severe outbreaks due to influenza A (H3N2).MethodsAfter local hospital staff and public health nurses detected influenza cases among the evacuees, an outbreak investigation was conducted in five ECs that had reported at least one influenza case from 23 March to 11 April 2011. Cases were confirmed by point-of-care tests and those residues were obtained and subjected to reverse transcription PCR and/or real time RT-PCR for sub-typing of influenza.ResultsThere were 105 confirmed cases detected during the study period with a mean attack rate of 5.3% (range, 0.8%–11.1%). An epidemiological tree for two ECs demonstrated same-room and familial links that accounted for 88.5% of cases. The majority of cases occurred in those aged 15-64 years, who were likely to have engaged in search and rescue activities. No deaths were reported in this outbreak. Familial link accounted for on average 40.5% of influenza cases in two ECs and rooms where two or more cases were reported accounted for on average 85% in those ECs. A combination of preventative measures, including case cohorting, personal hygiene, wearing masks, and early detection and treatment, were implemented during the outbreak period.ConclusionsInfluenza can cause outbreaks in a disaster setting when the disaster occurs during an epidemic influenza season. The transmission route is more likely to be associated with sharing room and space and with familial links. The importance of influenza surveillance and early treatments should be emphasized in EC settings for implementing preventive control measures.

Highlights

  • The Great East Japan Earthquake of magnitude 9.0 that struck on 11 March 2011 resulted in more than 18000 deaths or cases of missing persons

  • The first confirmed case was identified in evacuation centres (ECs) (A) on 18 March 2011, and further cases were reported from five additional ECs (Figure 1)

  • EC (B) recorded 60 influenzapositive cases which accounted for 57.1% of total cases [60/105], whereas EC (C) reported 31 cases, EC (A) reported 10 cases, and EC (D) and (E), where the first influenza cases were detected at later dates, reported only two cases each (Table 1)

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Summary

Introduction

The Great East Japan Earthquake of magnitude 9.0 that struck on 11 March 2011 resulted in more than 18000 deaths or cases of missing persons. At the time of the Great East Japan Earthquake on 11 March 2011, influenza A (H3N2) was still circulating and there was a heightened concern regarding severe outbreaks due to influenza A (H3N2). The coastal area of the Tohoku region, which was most severely affected by the tsunami, has a higher percentage of elderly residents than the national average and, an increase in the incidence of some diseases that affect the elderly, such as pneumonia [4], occurred after the earthquake. Infectious diseases that may cause outbreaks in post-disaster settings can be categorized into four groups: waterborne diseases, acute respiratory infections, vector-borne diseases, and infections as a result of wounds or injuries [5] Of these diseases, acute respiratory infections, including influenza, are among the most common that occur after natural disasters [6,7]. We describe the epidemiological characteristics of influenza in an EC setting

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