In 1882. Adolf Weil described disease which he observed two times in four patients in 1870. The simptoms were similar at all four patients and were very unique. Disease came sudden with fever, high temperature, tumor of splen and icterus. 1881. in Prague, Weiss described "Icterus catarrhalis" which could also be Weils disease. 1890. Globig describes Badeepidemie, a disease which showed lots of differences compared to Weil's disease. 1891. F. Muller described Schlamfieberepidemie in Schleisen, a disease with similar simptoms. Rimpau et al. described Feldfieber, which was a name that they ment for unicteric leptospiroses. The disease was given different names. Weil called it "Typhus biliosus nostras". Others called it "Maladie de Weil", Infectious icterus"...

Bacteriologists, and among them Robert Koch, after discovery of Weils disease tried to isolate etiologic agent with no success. Etiologic agent was first isolated in 1915. by Inada and Ido. They isolated Lepto from mine workers and named it Spirochaeta icterohaemorrhagiae. P. Uhlenhut and W. Fromme proved the existance of etiologic agent by inoculating blood from soldiers who suffered Weil's disease to guinea pigs. Animals died and they diagnosed lepto microscopicaly and named it Spirochaeta icterohaemorrhagiae (1915). Japaneese Miyajima, Ido, Hoki, Ito and Wani (1917) realized that rats are possible animal carries, by showing that 40% of theese carrie lepto in kidneys.