Plague has become a permanent problem in the western states.1 In fact, the investigations of 1935 and 1936 have conclusively shown that the endemic reservoir in the ground squirrel (Citellus beecheyi), first suspected in 1904 and proved in 1908 in California,2 now embraces large territories and new species of rodents (Citellus oregonus, Citellus armatus, Citellus Columbianus, Citellus grammurus, Citellus Richardsoni, Marmota flaviventris, Eutamias quadrivittatus and Cynomys parvidens) in Oregon, Idaho, Nevada, Utah and Montana. Renewed interest created by the discovery of extensive and destructive epidemics among squirrels in the foothills of the Sierra Nevadas and the recesses of the Warner Mountains in northeastern California in 1934 has doubtless been responsible for the recognition of a few cases of plague in human beings. These infections must be interpreted as accidents, as they involve occupational groups or vacationists who have in one way or another come in contact with animals.
MEYER KF, CONNOR CL, SMYTH FS, EDDIE B. CHRONIC RELAPSING LATENT MENINGEAL PLAGUE. Arch Intern Med (Chic). 1937;59(6):967-980. doi:10.1001/archinte.1937.00170220043003