To the Editor::—Failure to observe the occurrence of a disease assumed to be common should not be assumed to indicate its complete absence or the complete immunity to it of a people, unless they be entirely isolated. The comparative lack of cases (observed by physicians or nurses) of scarlet fever among Indians of the Southwest has been the basis for suggestions of natural immunity, both written and oral, for many years.
Frank and Elkin, having found 22 per cent positive reactions to the Dick test among 816 Indian children (750 Pueblo and 66 Navajo), concluded that they should be susceptible to the disease, and observed 8 cases in the region of Laguna, N. Mex., during 1945 (Am. J. Dis. Child. 71:477 [May] 1946). Wider and more detailed observation, in their opinion, probably would increase the recorded incidence of the disease in these people. The following observations among another