Hello! Congrats on making a functional product under time pressure :).

Here's an idea for extending gameplay: the player has no real decisions to make, so there's no tension in the gameplay. Introducing limited resources and different tradeoffs to using them will increase the complexity of the game and will make the player experiment, learn and handle dilemmas.

Say there's limited time - the host is defending against you, and you won't live long unless you do something about it. Also, you can only infect three times. In addition, the infected entities will spread the infection when they touch another one. 

Now the player has to observe the trajectories of the entities in order to figure out if they will intersect with another one. More so, now the player needs to decide if he wants to spend time to get into a better position, to spend his infection charge in a more effective manner (on an entity that has a greater potential of infecting more times), or would they rather prioritize time and infect sooner. 

Nothing too hard to implement, but you give the player something to chew on.

Here's a fun read that talks about decisionmaking in games: "Players Making Decisions" by Zack Hiwiller. Good luck in your gamemaking journey :).