I would see to it that I had a substantial file of fraud on quite a number of employees, then in one fell swoop I would fire them all at the same time on the same date.
If that didn't awaken the other employees I would repeat it until I had a solid and reliable employee base from which to operate my business.
The last thing I would want to do is open my company up to a possible civil suit for a supervisor revealing confidential medical information about an employee.
I like that suggestion. And it might work; even in a union environment.