Interesting concept. Having worked on projects that require robust pathfinding solutions, I respect that you were able to complete this within a game jam timeframe. Pathfinding is no joke lol.
Biggest complaint I have is that there wasn't really anything preventing me from reaching the goal except for the time it took to draw the right cards. As far as I can tell from a single playthrough, the enemies don't really do anything except attack your hosts. One of them wandered past my unguarded infection site at one point but didn't pause to attack or otherwise hinder my expansion.
All said, this is definitely a place you could build from if you wanted to expand the game. Creating more hindrances to the parasite's expansion, allowing deck customization/some form of meta-progression, procedurally generated levels, etc. would all contribute to making the game feel fuller and more rewarding.
Congratulations on completing the game jam and keep up the great work!