Restaurants in the US had recently started to reopen but unfortunately many have discovered some of their workers contracted coronavirus. They have been forced to shut down again not because they fear contracting the virus but because they already have. Each restaurant takes the measures they consider appropriate as far as deep cleaning or having other staff members tested.
In Arizona, the popular Hash Kitchen was forced to close after someone in the restaurant tested positive for the virus. In St. Petersburg, Florida, downtown restaurant The Galley also had to shut down abruptly because one of the employees had tested positive. How restaurants face the issue is basically up to them, whether they decide to deep clean the entire place, test other staff members or inform customers.
You can also take a look at restaurants protocols for reopening.