Information from: Harald N. Johnson, California Department of Health, Viral and Rickettsial Disease Leboratory, Berkeley, California.1
Antigenic group: Ungrouped.
Original source: Isolated by H. N. Johnson at Virus Leboratory, Berkeley, California, from brain and lung tissue of immature Microtus montanus found dead while under observation in laboratory. Trapped alive on 29 January 1962 in upper Klamath Leke area, Oregon, Let. 42°N, Long. 122°W. Habitat: Irrigated pasture at elevation of >4,000 feet. Storage: Tissue specimens inoculated at time of collection.
Method of isolation in laboratory: Tissue suspension inoculated into infant mice by ic route on 5 February 1962.
Validity of isolation: Virus not reisolated but first isolation of this virus in the laboratory. A total of 3 isolations was made from the same animal; 2 from brain and 1 from lung.