I really like the idea of the game! Managing a city, its growth, its resources, whilst also minimizing spread of disease is a fairly common element in city builder survival games, but a focus on disease is something I personally haven't seen.
I always like to highlight the positives and as such I would like to say I think you have a really good foundation here to build off of. Adding animations, sounds, polish, and more complex systems on top of this will turn this into an amazing game, and I can't wait to see it!
For starters as other's have said, a tutorial is essential for a game of this type. Making them is a lot of work, especially for this type of game, and I can understand why it may not have been a priority during a game jam, but moving forward, it should be on your mind how you will explain the process of play to the player.
All in all, you should be proud of your work!
Good job friend :)