Flea re-infestation possible from other apartments?

I live on the third floor of an apartment building with 12 units (4 on each floor), with at least 5 of the units having dogs. My indoor-only cats came up with fleas July 5th and by then I had an infestation. I treated them with Advantage II, vacuum daily all the areas that they go, wash all bedding and treated once myself completely with Knockout spray (permethrin, Nylar), once by an exterminator hired by the apartments last Tuesday (not sure what he used but smelled a lot like what I used) and I spot treated the hot spots again yesterday with Knockout. Unfortunately I seem to be having more biting adults at night than when I started. Is it possible that I am seeing re-infestation from other apartments or do you think I just need to ride out the evening insanity and it will end soon? I wasn’t home when the exterminator was there and I am wondering whether he treated the other apartments, as they said he was going to do. I am not sure that other apartments were infested, but a few neighbors with dogs reported fleas and were much less upset with them than I was. Thanks again for all your help on behalf of all of us wanting this to end!