A couple of posts back I tried to rationalize how it could have occured but I was rather long winded, as Osiris pointed out. ; )
Basically I was thinking that because the zombies intended to eat the people they brought in to
the arena, they did not infect them or taint the meat. I know that they were piling some of their own dead outside the arena, but it seemed like the ones in the pile that
Riley and
Angel climbed in was full of human corpses that hadn't turned. I don't think
Datu had direct contact with the blood, at least none that was introduced into his blood stream.