Well, if you take into concideration that there might have been a Lab in the center of the city where experiments with genes or diseases might have taken place, Bio enginered zombies are a possiblity. But on the Queen Zombie topic, think of it as a bee hive or ant colony, the zombies are like the drones or scavengers, there must be a central intelegence telling them what to do. There might be a queen and then the queen has her lieutenants, or "officers" who work in the field carrying out her orders, like the man in the pin striped suit, aka the one with the markings.
I rest my case