Would China be able to prevent a US citizen from getting out of their country? Somehow I find it hard to imagine a scenario where the Chinese government would be able to say: "Ok, we have this US citizen here that we believe is infected with a new virus. We're going to keep him in lockdown until further notice."
If anything Xi Xinpig would have the citizen sent back over to North America just to spread the virus, because he's a murderous piece of shit who wants us all dead for petty as fuck reasons. That's why we need to kill him before he kills anymore of us, and drag it out so he fucking suffers.