About 3-4 weeks ago, I was asking anyone I spoke to why #Covid19 didn't seem to be taking off outside China. There were <500 cases. Many very seasoned epidemiologists were puzzled. But a couple said: it takes time for an outbreak to take off.
(data: @WHO, graph: mine) pic.twitter.com/h7cFXC5nl6

— Helen Branswell 🇨🇦 (@HelenBranswell) March 8, 2020