(Alright, so this is all I can remember from this movie, aside from some minor scenes)
A group of mercenaries are charged with going into a university to retrieve an experimental virus (I can’t remember why it’s there), when on their way they get attacked by a group of zombies during which, one of the zombies tears through the armor of one of the mercs, after being killed the leader says that the zombies are ‘adapting’ and have grown sharper teeth to tear through armor.

(the other scene)

One of the last surviving mercs locks a wounded person in a room to try to keep them safe, but, when they come back they are infected (they weren’t bitten before), that’s when they find out mosquitoes can carry the virus.

If it helps this was part of a series of movies and I believe this is the seventh movie.