[Infectious disease surveillance in Miyagi after the Great East Japan Earthquake]

The Great East Japan Earthquake, which occurred on March 11, 2011, damaged many health facilities and compelled many inhabitants to live in evacuation centers. For the purpose of monitoring infectious disease outbreaks, infectious disease surveillance targeted at evacuation centers was established in Miyagi Prefecture. In this study, we summarized the monitoring activities of infectious diseases through this surveillance after the earthquake.

Infectious disease surveillance was implemented from March 18 to November 6, 2011. The surveillance consisted of two phases (hereafter, surveillance 1 and 2) reflecting the difference in frequencies of reporting as well as the number of targeted diseases. Surveillance 1 operated between March 18 and May 13, 2011, and Surveillance 2 operated between May 10 and November 6, 2011. We reviewed the number of cases reported, the number of evacuation centers, and demographic information of evacuees with the surveillance.

In Surveillance 1, there were 8,737 reported cases; 84% of them were acute respiratory symptoms, and 16% were acute digestive symptoms. Only 4.4% of evacuation centers were covered by the surveillance one week after the earthquake. In Surveillance 2, 1,339 cases were reported; 82% of them were acute respiratory symptoms, and 13% were acute digestive symptoms. Surveillance 2 revealed that the proportion of children aged 5 years and younger was lower than that of other age groups in all targeted diseases. No particular outbreaks were detected through those surveillances.

Infectious disease surveillance operated from one week after the earthquake to the closure of all evacuation centers in Miyagi Prefecture. No outbreaks were detected in that period. However, low coverage of evacuation centers just after the earthquake as well as skewed frequencies of reported syndromes draw attention to the improvement of the early warning system. It is important to coordinate with the medical aid team that visits the evacuation centers on a regular basis and to obtain information about the characteristics of evacuees. It is necessary to establish a surveillance system that can monitor infectious disease efficiently from an early phase.