I don't have a good answer, but I have a French client who also employs an American guy whose health is very weak (but I think it's more bouts of 2 weeks without being able to work), and my client just patiently waits for him to be able to come back. He even gives him French healthcare perks out of (the corp.) pocket, because it'd be more complicated to involve an external insurance (in France the salary is insured too, not just the medical bills).