Shelley Singer has been the primary caregiver for her husband, Michael Gross, since he was diagnosed with Alzheimer’s disease four years ago. Then came the coronavirus pandemic. “It’s very difficult to live with someone with dementia, and I know how fortunate I am to be able to have help from caregivers during the day,” said Singer, 70, who lives in Bethesda, Md. “Dealing with someone with dementia in an unprecedented crisis — there’s just no road map for that.”