have you looked into how long a flea can survive without a host, I think the amount of time is quite surprising, when my dkg had the fleas at home I did look into it, can't remember the exact time frame but was quite surprised at not only how fast they multiply but also how long they can survive with out the host. You may also want to look into how they live off your bites? is it possible they are staying alive longer by biting the human and getting a little flea nutrients from those bites? I know and serious infestation happens fast and can take quite a bit of effort to get rid of, alot more dif than just "getting rid of the animal". My daycare family "bombed" their house and left town for the weekend, no joke!!!!!!!!! Not even sure if that did the trick, lots of sprays and vacuuming went on that week as well. YUCK!!