And you cannot prove the negative of not having mitigation but reason and logic would lead almost anyone with any sense to know that if the US has this many cases, and the same with Italy and Spain, with some harsh mitigation then there would be many, many more deaths and cases without mitigation.
Logically, if the virus is new and novel (true), and if it spreads from human to human through close contact (true), and if the virus spreads at a fairly high rate (true as far as measure at about 1 to 2 or 3 iirc), and if infected people without symptoms can spread the virus (true), then the virus will spread very fast if people are in close contact all the normal times.
This logic is no different than using the logical argument if rain only comes from clouds (true), and if it is not cloudy (which is true at times), then it will not rain at that time. If-If-Then reasoning.