It is revealed in the Ryder White campaign he is not the Voice, but in fact being told what to do by Kevin/Charon who is the real Voice.
During the first phase of the final battle on the roof, colonel White will fire at the player from the helipad while the player fights his BIDF Soldiers. However, he cannot be harmed by the player, much like a regular survivor.
During Ryder White's Campaign, it appears that he is immune to the infection due to him not contracting the disease despite fighting through so many zombies. It is possible that the "antidote" he injected himself with actually destroyed his immunity to the infection. Alternatively, this may simply be a case of separation between gameplay and storyline, with colonel White managing to fight his way across the island without ever being bitten.
In Ryder White's Campaign, it is revealed that Ryder has two daughters named Kate and Pamela.