They don't execute axe murderers in this country. There's no way they'd execute a Typhoid Gary. And the original request was to apply public health principles, not criminal law.
However, in theory, you're right. Knowing transmission of a fatal virus is, in effect, homicide with malice aforethought. That makes it first-degree murder. However, the victim would have to die before that charge could be brought.
I disagree. Once he's infected the victim is already dead. We're just waiting for rigor mortis to set in. GRIDS is incurable.