This is really cool! Your use of the theme is really fun and engaging, and it completely changes my playstyle for shooter games like these. Sadly, I think the mechanic inherently makes the game flawed because it becomes more valuable to tank and sprint through the level instead of kill the enemies, but the endless mode makes that less of a problem. I think if my health didn't drain over time and/or when I shoot, I'd be more inclined to kill the enemies instead of suiciding and then taking them over, but that's a relatively small issue.
The movement and gameplay feel great, it's very intuitive and satisfying to move, shoot, and infect; the art, music, and story all work together very well to keep me immersed, and I had a fun time. Nice job!