As always, Dr. Coyner has some great advice.
One thing you might consider is to pick up a flea area treatment (spray, not fogger or bomb) with an insect growth regulator, like Dr. Coyner mentioned. Before applying it, vacuum the area very well, then apply. Continue to vacuum at least once daily for 2 weeks and then reapply the area treatment.
The fleas you are seeing now are coming from the hidden places Dr. Coyner mentioned plus the cocoons that are hatching out. There really isn't a flea product that can kill the cocoon stage and they can remain dormant for about 5 months. It seems that the vibrations, sound, and often lights associated with vaccuming can stimulate the coccons to hatch into adults. And this hatching is quick! Usually happens in about 1 second (much faster than those old slides of butterflies hatching from the cocoons that we saw in grade school!)
So...vaccumming will help adult fleas to hatch, who, being hungry, will look for the pets and then be killed by the Frontline you have already applied. And, in case you didn't think of it already, please make sure all the pets in the household (dogs and cats) are being treated.
I have had success with both Frontline and Advantage, and both products offer some data that their product kills adults and also affects flea egg hatching. Frontline Plus has an insect growth regulator as well, which definitely prevents flea eggs from hatching. The key is to use the products every 3-4 weeks on all pets, and to treat the environment, because one flea on the pet means 100 eggs in the environment, which continuously hatch and reinfest the pets. Flea bombs are not bery helpful, because they broadcast the spray non-specifically over furniture and exposed flooring, but the fleas hide under furniture and in crevices. I recommend using a flea spray or carpet powder that has both an insecticide for the adults (pyrethrin, permethrin) and an insect growth regulator to prevent flea egg hatching (methoprene or nylar). The product should be applied to all places that the animals tend to lie, under furniture, and on cracks and baseboards. You may want to wait another week or two before applying more insecticide to the home since the bomb was just used last week, make sure to follow label instructions.
Good luck,
Kimberly Coyner, DVM DACVD