D. Epidemics of the Reduced Region
After the disruption of the aboriginal epidemic region, the Indians of central and southern Mexico under Spanish control continued to suffer from the high mortality of infectious epidemics. These are worth describing briefly, because it is possible that one or more of them may have jumped the devastated and depopulated regions and reached the northern Pimans especially since two of them were apparently the most severe epidemics ever experienced in Mexico (after the initial 1520 holocaust, at least).
1. Epidemic of 1545
The third great epidemic following Spanish conquest occurred in 1545. The infectious agent is unknown, but produced a hemorrhagic fever, possibly typhus (Zinsser 1934:256). It could even have been the specific hemorrhagic fever recently identified in Korea, which may have existed for a long time previously. The mortality in central Mexico was estimated at 150,000 among the Tlaxcalan nation alone (Ocaranza 1934:84) which was a relatively small one in population terms. This epidemic has been termed one of the two most severe suffered in Mexico in historic times (Bancroft 1883:III:756).
2. The Matlazahuatl Epidemic of 1576
After 1545 the Indians enjoyed some respite from serious epidemics although introduced infectious diseases were undoubtedly becoming endemic. There was another epidemic of unknown severity and type in 1564 (Ocaranza 1934:85) but it was not until 1576 that another major epidemic carried off millions of Indians. The estimated mortality within the area under Spanish control was two million natives (Bancroft 1883:III:353). The disease was similar to the one which had caused the epidemic in 1545, and has been tentatively identified as typhus (Ocaranza 1934:85; Zinsser 1934:257).
Although this seems to have been the most severe epidemic of all in terms of total mortality in New Spain, there is some indication that its geographic spread was less than in 45other epidemics. Its worst effects may have been confined to the area of the Archdiocese of Mexico, lessening in Puebla and Michoacan (Alegre 1841:II:110) and perhaps not spreading much beyond.
3. The Measles Epidemic of 1595-1596
Another epidemic struck in 1538, but seems to have been localized in central Mexico (Ocaranza 1934:85). Then in 1595 measles reached epidemic proportions again, apparently in a particularly virulent form causing frequent complications. This may actually have been a multiple-cause epidemic, with typhus contributing to the mortality (Zinsser 1934:257), and may have been a multi-phase epidemic, since contagion was reported among the Sinaloa Indians in 1593 (Dunne 1944:111).
These were the final serious epidemics of which record has been found which occurred during the decades when the northern Pimans were so far as known cut off from the Spanish epidemic area.