'Actively' seems to be accurate for the scenario when one is choosing to make body conducive to incubate virus, or already incubating them (albeit unknowingly if asymptomatic).

[Edit] And if you meant active in context of 'Active shooter', then still use of the word active is not wrong. Virus laden body is like carrying a concealed gun which is on 'auto pilot', it is actively spraying bullets; it IS active all the while.

I can't think of a single person I know that hasn't ducked down to the shops to pick something up when they have the flu. By your definition, they are actively attempting to cause harm to others - which is an interesting take.

Even before covid, I would always wear a mask if I had a flu and would try as much as possible not to go to shops or pick up anything. A lot of people I know do the same.

I haven’t “ducked down to the shops” when I’m ill. It’s not that hard to keep necessities around.