Probably best to wait IMO. I think I'm having issues with my B178 world I continued with 180. I've only hit one POI but there were no zombies at all...just one vulture on the roof that didn't even bother to take flight. I just walked over, crouched down, looked him in the beady little eye then stuck a machete in it. Very satisfying but a little anti-climactic.
Edit: Have since ran through a couple more POI's with no issues so maybe it was specific to that POI (small Working Stiff out in the country with a car crashed through one of the big windows).