10% would be a disaster. 40%-70% would only be possible with a complete failure of our healthcare and public health infrastructure and a lack of any response to contain outbreaks. It would also require an immensely uninformed and ignorant public that refused to take personal precautions. Even if the government fails COMPLETELY, no one wants to be infected with a virus that is life threatening, and INDIVIDUALS will take precautions themselves once if they see a major breakout that overwhelms the system.
The only places where such failures might happen are backward countries like Iran and North Korea, and 3rd world sh**holes.
Yet, the US government took it’s sweet time stopping flights. We still haven’t stopped enough. It’s taking individual companies to decide on their own. American Airlines had to have basically a walk out over Italy flights before they stopped.