The green "virus" enemies that spread don't show up. Fix?

[PillowPenguins]

The title pretty much says everything. I can still shoot them, and worse, be killed by them, and I see the particle's come off of them when they die, but they do not show up at all and I frequently crash into them. I tried reinstalling the game and messing around with the visual settings but nothing works. Anyone else have this problem or know how to fix it?