At what point can you make an OSHA complaint that your employer is failing to provide you a safe (disease-free) workplace?
While you’re at it, file a complaint about them making you drive to work in a car.
Never, but taking these actions in this situation is definitely negligence at best. It's like running a hospital forcing people to work without providing soap or hand sanitizer.
It's not so much about certifying it as disease free and more about certifying it as unsafe.
If your employer forced you to drive through floodwaters, you'd probably have a valid OHSA complaint.