High prevalence of deep vein thrombosis in tsunami-flooded shelters established after the great East-Japan earthquake.

High prevalence of deep vein thrombosis (DVT) in disaster shelters has been reported in the aftermath of earthquakes in Japan. Calf DVT was examined using sonography in the shelters after the Great East Japan earthquake on March 11, 2011. By the end of July 2011, 701 out of 8,630 evacuees suspected with calf DVT, judged by inspections or medical interviews, were examined in 32 shelters, and 190 evacuees were confirmed to have calf DVT. The prevalence of DVT was 2.20%, which was 200 times higher than the usual incidence in Japan. The DVT prevalence seemed to decrease with time. By the end of May, a significantly higher prevalence of DVT was found in tsunami-flooded shelters (109 of 3,871 evacuees; 2.82%) than in non-flooded shelters (53 of 3,155 evacuees; 1.68%). After June, its prevalence was still higher (18/541; 3.33%) in tsunami-flooded shelters than in non-flooded shelters (10/1063; 0.94%). The cause of the high prevalence of DVT was supposed to be dehydration due to the delay in supplying drinking water, vomiting, and diarrhea experienced by the evacuees because of a shortage of clean water to wash their hands. Dehydration was especially noticed in women because they restricted themselves of water intake to avoid using unsanitary toilet facilities. Moreover, crowded shelters restricted the mobility of elderly people, which would exacerbate the prevalence of DVT. Those deteriorated and crowded shelters were observed in tsunami-flooded areas. Therefore, long-term shelters should not be set up in flooded areas after tsunami.