"In a context that includes Ebola and MERS, the Covid-19 death rates are much closer to those of the flu, and it’s understandable why people find the comparison reassuring."

"Compare Covid-19 with just the flu, though, and it becomes clear how different they are. The 61,099 flu-related deaths in the U.S. during the severe flu season of 2017-2018 amounted to 0.14% of the estimated 44.8 million cases of influenza-like illness. There were also an estimated flu-related 808,129 hospitalizations, for a rate of 1.8%. Assume a Covid-19 outbreak of similar size in the U.S., multiply the death and hospitalization estimates by five or 10, and you get some really scary numbers: 300,000 to 600,000 deaths, and 4 million to 8 million hospitalizations in a country that has 924,107 staffed hospital beds. Multiply by 40 and, well, forget about it. Also, death rates would go higher if the hospital system is overwhelmed, as happened in the Chinese province of Hubei where Covid-19’s spread began and seems to be happening in Iran now. That’s one reason that slowing the spread is important even if it turns out the disease can’t be stopped. Could Covid-19 really spread as widely as the flu? If allowed to, sure. The standard metric for infectiousness is what’s called the reproduction number, or R0. It is usually pronounced 'R naught,' and the zero after the R should be rendered in subscript, but it’s a simple enough concept. An R0 of one means each person with the disease can be expected to infect one more person. If the number dips below one, the disease will peter out. If it gets much above one, the disease can spread rapidly...."

From "How Bad Is the Coronavirus? Let’s Run the Numbers/The risks posed by Covid-19 — and the possibilities for getting it under control — become clearer with some simple math" (Bloomberg). The graph shows the estimated R0 for Covid-19 at 2.8 and for seasonal flu at 1.3.