Whole shop staff down with viral fever one after another. How do I break the chain?

Started with one boy at the counter two weeks ago. Now 6 out of 9 staff have had it, fever, body pain, cough. They take two days off, come back, and the next one falls sick. I also had it for three days. Shop is a closed space with an AC and one door. Customers come and go all day. I have started keeping sanitizer and told everyone to wear masks but half of them don't. Is there anything practical a small shop owner can do? Should I close for two days and get it cleaned? Losing business either way, would rather lose it once than six times.