An R0=3.8 means that it exceeds SARS’s modest 0.49 viral attack rate by 7.75x - almost 8 fold! A virus that spreads 8 faster than SARS ... Even if overestimated R0, it is still the worst seen in history.
The typical R0 attack rate for the seasonal flu is around R0=1.28. The 2009 flu pandemic R0=1.48. The 1918 Spanish Flu 1.8. Infected 500,000,000 The 1.8 level killed 50,000,000-100,000,000 people, 675,000 in the US.
Only 5% of Wusan infections identified - lending credence to the 90,000 infections report
Can be contagious with NO symptoms showing. No fever often reported when infection identified, can spread through eyes (goggles needed), removing ear wax leaves infection channel.