I don't care if you can't control them in combat, but if party size is four it seems to go completely against what makes sense for this sort of game. If I understand what this kind of game is. I'd rather see something where you lose guys left and right, not do the save reload fandango because one of the tiny number of party members got infected.
If it's a survival game there should be real danger, and you should be suffering attrition over time until you win the game. It should be like Xcom where you lose a guy almost every battle, and on top of that lose guys due to disease, infection by zombie, accident, on a pretty regular basis. Maybe send them out in parties to forage and not everyone always comes back, but the results get calculated at the start of the day or week so you can't reload.