Can fleas carry blood borne diseases?

My cat had flea's, but I have treated them with Frontline, obviously there are probably eggs and flea dirt still around the house (I hoover regularly). I am concerned that fleas may possibly bite humans from around where I live and then come into my house and leave their flea dirt lying around, therefore I have human blood around my house. I know this sounds crazy but can fleas or flea dirt carry any diseases? I have a 3 year old who loves to play on the floor and a 5 month old who is starting to crawl and I am concerned for their health, could they catch anything (hepatitis etc). I could never get rid of my cat so I need to know the solutions