December 18, 2013; 4:02 PM ET
Damp and chilly weather is in store for Seattle this week, and snow may fly by Friday morning. more >
Mixed rain and snow before dawn Friday; watch for icy spots
The sheer number of people, their interactions with animals and ecosystems, and the increase in international trade and travel are all factors that will likely change the way humanity deals with preventing and treating epidemics, experts say.