I don't know why it took me so long, but I bought a flea comb today. It was amazing how many fleas I got off of my three cats. If you don't have one I would get one. My cats enjoyed the combing and I enjoyed getting rid of those pests!
It would be a good idea to take your cats to the vet to get a Frontline or Advantage flea treatment too. At any one time your home will contain 10 times more fleas than you find on the cats, as the fleas live in the carpets, curtains, sofas etc and only jump on the cats to feed. Also, flea combs don't catch the eggs, so although it is good to use a comb, it is only a temporary measure and you need something that will kill each flea as it tries to feed. Flea powders and collars can be ineffective and also some cats react badly to them. Do make a vet visit so your cats will be permanently comfortable.
Flea combs may get some of the fleas but they don't kill the eggs, and they will continue hatching more fleas and these will lay more eggs. One flea can lay 40 eggs per day! Fleas can be really tough to get rid of, and unfortunately most of the store-bought products (Flea collars, shampoos, pills) won't completely destroy them. Trust me I've gone through all this myself! After trying lots of different stuff, I saw the vet and he recommended a topical treatment- called Advocate. I also used a spray for my house that kills the flea eggs. My kitty is now flea free : )
Severe flea infestations can make cats very sick, and sometimes they can even kill cats, especially kittens or older cats. Also, cats can get tapeworm from eating flea eggs, so they may need to be treated for that too.
Maybe give your vet a call and see what he says.
Good luck getting rid of those nasty fleas!