The strain was isolated in Czechoslovakia from the kidney of a yellow-necked field mouse (Apodemus flavicollis) in 1953 (Kmety, 1954). It was later submitted to factor analysis and described as a new serovar named jalna, ref. strain Jalna (Kmety, 1960).
In Dikken and Kmety's publication in represents the subgroup Jalna (Dikken, Kmety, 1978).