Both of mine were born this time of year... IMO, I would just say "if you aren't feeling 100% please don't come near the baby"... Kids actually tend to be better than adults sometimes!
The dynamic your friend is dealing with though is a medical issue which is going to require a trip to the hospital for corrective work. There's only so much cleaning/sanitizing that the hospital can do, but there is going to be exposure there to many people and they won't know if the kid before them in the hospital room was there for being sick with the flu or surgery.. Stick with "common sense". Hand washing only goes so far when people are rubbing their nose with their wrist, touching their hand to their hair, biting nails, touching door knobs, using a "community" hand towel in the bathroom, etc. In other words, there is very little that can be done. Switch out the bathroom towels with a roll of paper towels or individual disposable towels. Remember that hand sanitizer DOES NOT EVER replace PROPER HAND WASHING!