Pretty damn filthy. At least, if it’s half as filthy as my daughter’s science fair project suggests:
In addition to our toilet seat and computer keyboard, our daughter swabbed and tested her own mouth, under my wife’s fingernails, the TV remote control, and the telephone. She rubbed each bacteria-laden swab in a solution in a Petri dish, and left all of them in a dark drawer for a week. Her hypothesis was that the object that had the most bacteria was the telephone. The experimental result for the most bacteria-ridden area discovered in the house?
Under my wife’s fingernails.