The R0 (infectivity level) of Wuhan coronavirus is thought to be between 1.4 and 2.5. For comparison, the R0 of seasonal flu is around 1.3. The mortality rate of Wuhan Coronavirus is possibly 2.5-5 percent. The mortality rate of seasonal flu is .01 percent. This thing is potentially twice as infectious as the seasonal flu (which is already really infectious), and 250 to 500 times more deadly. It is not an exaggeration that if this gets out of control it could kill tens of millions or more and could potentially be the deadliest plague (in terms of raw fatality numbers) in history.