I have a high level of confidence that this is a bioweapon
At 3-4% fatality rate? Must be US made.

Look closer.
Closer to what mate? According to the recent stats at 181k confirmed cases and 7k deaths, it's less than 4%. However, according to scientists, the number of infected people is waay higher than official numbers. What's your point exactly?
The virus is asymptomatic for 2 weeks and the number of infected has a doubling time of 6 days. This gives us, roughly, death/(currentinfected/4). Or in other words multiply the 4% by 4 for the correct number.
The second main method to calculate it is death/(death+cured). Pick whichever one you prefer.