A must read for all employers, both public and private, is the US Equal Employment Opportunity Commission's publication "What You Should Know About COVID-19 and the ADA, the Rehabilitation Act, and Other EEO Laws."
In plain English, if you have an employee with a pre-existing disability that either "puts her at greater risk during this pandemic" or, if such disability will be "exacerbated by the pandemic," and such employee requests a reasonable accommodation, then, you better either grant that request or engage in the "interactive process" to avoid getting sued.
Be warned - the lawsuits are coming.
