you're clearly not able to judge much if you dont know the basics of a standard cold.
Some of us have an advanced education and a passion for other things than looking straight ahead and reading PAL's,.
I agree with your initial advice about not smoking and eating well but Unless your advanced education is a medical degree then your unqualified. How do you know he does not have some condition that weakens his immune system?
We have a mechanic in my shop that is out sick often, it's not my job to judge him or discipline him. I fix trucks, after 8-10 hours I go home. If something does not get done because of other mechanics calling out then that is a UPS problem not a me problem.