Well yes, obviously—but Mexican epidemiologist Rodolfo Acuña-Soto thinks that the 16th Century plague that reduced the Aztec population from 22 million to 2 million was
not smallpox brought over by the Spaniards. Aztec historians of the time referred to it by a different name than smallpox, with which they were familiar(!), and, after 12 years of research, Acuña-Soto concurs.