Yosemite is right. If one animal in the household has fleas, I would bet your bottom dollar the others do too. So, give everyone a dose of Frontline at the same time, then spray your carpet, dry it, and then vaccuum. Spray, wash, and dry all bedding, blankets, couch cushions, towels, WHATEVER they may be living on...then toss your vacuum bag OUTSIDE in the dumpster. The other easier option is a flea bomb. Send your pets to a responsible family member or friend for a day or two, and then set the bomb off. When you return, vacuum everything, throw the bag OUTSIDE in the dumpster, and your pets may return home. Frontline will kill the fleas on your pets within 24 hours...you will actually see many of the bugs retreating toward the pets tail before they croak.
Don't panic! It's treatable! It's easy!!!