As Covid-19 restrictions in various regions of the U.S. begin to loosen, employers may face the prospect that some of their employees may not want to return to work because of potential health risks. Employees may feel that they have the right to refuse to work in hazardous conditions; from an OSHA perspective, they would be protected from retaliation if they can prove that the hazard would involve "imminent danger." While it is not clear Covid-19 is an imminent danger, a 1980 case allows employers to not pay employees who refuse to return to work. From an NLRA perspective, employees who refuse to work to work, or go on strike, may be protected if the conduct constitutes "protected concerted activity" - conduct that is based on behalf of a group, not for individual concerns.
See "As businesses reopen amidst Covid-19 concerns, can employees reject returning to work?", C. Thomas Davis, Ruthie L. Goodboe, and John F. Martin, National Law Review, May 27, 2020