Thematically relevant, but also perhaps the more obvious idea. Mechanically speaking, it doesn't stray very far from spraying bullets for the most part, though the uphill fight against contagion was a good twist. On the whole, the package comes together for a good balance, and it feels like it is exactly what it needed to be.
I think the more intuitive control choice would be to have right click simply be use of the mask. In implementation, it could just prioritize which button was either pressed first or pressed last when both are held down. Apart from that, it controlled very smoothly.
The sick-emoticon was a cute touch, and all the visuals read well on screen, even when moving quickly. The music was fitting and gave a matching vibe as well. So nice choices there. I wish I could give a higher score for polish & production, but that's limited by the fact that they are pre-existing assets.
Solid execution. It plays well and was fun overall. Good work!