There was another actual event at the end of Burning Crusade with similar mechanics to this. Plagued grain barrels spawned in cities, and players who interacted with them would die and spawn as an infected zombie. They were able to attack other players and spread the infection in doing so. My memory is pretty hazy since it happened so long ago, but in Shattrath (a high level neutral city), the zombies weren’t able to be attacked (probably due to pvp flags being forced off within the city limits), but in the faction cities, they were. This led to mobs of zombies roving around in Shattrath, pouncing on any unfortunate player they could find, where players in the faction cities formed subjugation squads and would patrol around, exterminating any zombies in sight.

Something else interesting was zombies gained access to another language (Zombie), and since Shattrath accommodated both player factions, you were able to speak to zombified members of the opposing faction.