By 1950, that had changed enormously, and there's been an explosion of the deer herd since then. The fact that both deforestation and reforestation can cause epidemics points to the danger of generalizing about the relationship of environmental change to disease. Global warming, on top of population growth, soaring international travel, and the breakdown in public health services makes for a miserable combination. Spielman paused, uncharacteristically, then responded. I can't think of anything that qualifies as good news.
Pathogens often jump from animals to people.