It's very clearly not murder; that'd set really bad precedents. You might be able to pull off something like involuntary manslaughter, but I tend to doubt it.
And if such persecution flies (which I doubt and really hope it does not), do not forget sweeping in as suspects for involuntary manslaugter those folks who, in the years past, came to work sick. Flu complications are deadly and kill many people, too.
I wonder if a civil prosecution might be easier. Have people pay for others' loss of wages, medical expenses, the support of dependents of people they caused to kill, etc, when they can be shown to have caused the spread and been irresponsible, to a civil burden of proof.
Two possible problems:
1) It might hurt tracing efforts if people are worried about being prosecuted (ie. people "clam up"). For example, this particular story might not be known at all. Hurting tracing harms public health, so this might be a good enough reason not to go after irresponsible people on the basis of tracing infections at all.
2) I'm not aware of the law ever holding anyone responsible for non-deliberate infection. New legal ground would have to be broken in this area.
(2) is a direct consequence of (1). Remember, until this year public health experts were always pointing out how shaming people in a public health context is highly counterproductive. People won't engage with the health system if they fear being punished for doing so. And with communicable disease that means there will be more spread.
With the extreme indifference to human life, and the knowledge that they could be causing "bodily harm" even if they think the odds of death are remote, we could try for second-degree murder.
It would fall under behavior matching something like likely to cause serious injury or death with reckless disregard or depraved indifference to the safety of others, which in most states would be straight manslaughter or low-degree murder.
