Back in 2016 this was teased, almost 5 years later and its still not in. I can understand that the game is "fininshed" and the team is smaller now and might have other priorities, but I feel like infected has been neglected for years now even though its an essential part of the game.
Right now everybody deal with infected the same way, as a nuisance not a threat, all you do is have the infected follow you into a house close the door and then carry on. It would make the game much more interesting if infected could break out or even crack open the door to your car and attack/pull you out so its no longer a mobile safezone.