Every pet owner should know about the dangers presented by fleas. They can attach themselves to your dog or cat, then hop inside and multiply like crazy as they make their way into your carpet and furniture. In addition to bites, they can also carry diseases.
But even if you don't have pets, you could "inherit" them from your apartment's previous renter if the problem wasn't taken care of. Your neighbors' pets may have fleas as well. But while they can be very stubborn, fleas aren't impossible to get rid of.
Here's what you do: First, if you have pets, get them treated with a bath or spray. Make sure they're on preventive flea medicine. Clean and vacuum any beds where your pet may sleep.
The pets are only half the battle, however: Flea eggs can be all over your apartment. (Gross.) Get a decent vacuum cleaner and run it everywhere, including your couches. Then strip the sheets and wash them in hot water. If all else fails, you may have to set off insecticide flea bombs.