Looking back over the last not even 20 years, with the examples of SARS and pandemic influenza; another coronavirus different from SARS, different from this one, the Middle East respiratory syndrome; avian influenza that pops up time to time in China; and Ebola, all of those are happening at a frequency we never would have imagined 20 or 50 years ago. I think it's happening as we encroach upon the natural reservoirs, encroach upon animal reservoirs. Also we can spread things so much more quickly now because of travel, things that would never have come away from a rural area are now in a different part of the world within 24 hours.
On April 30th, 2020. See this statement in context.