[\'Tsuchiura Public Health Center of Ibaraki Prefectural Government, Tsuchiura 300-0812, Japan.\', \'Fujiidera Public Health Center of Osaka Prefectural Government, Fujiidera 583-0024, Japan.\']
Long Diagnostic Delay with Unknown Transmission Route Inversely Correlates with the Subsequent Doubling Time of Coronavirus Disease 2019 in Japan, February-March 2020.