"Scientists - not just scientists, anyone - can fall into the trap of thinking that once we have a certain amount of knowledge, we really understand how things work, we don't need to question it anymore. But the lessons of these epidemics is that as much as we've learned and as much as we know there were always these unknowns out there, or these partial understandings, and we only learned what we're missing when the next epidemic comes along." - Mark Honigsbaum