You simply have to have the known numbers of confirmed dead and recovered patients.
The way you used it "1 / (1 + 0) = 100%" means just "the knowledge used in the formula is that one patient died, zero recovered." In that case, yes, the fatality rate is "everybody dies." But using the sample of 1 is of course not meaningful for any statistics, not only for that formula.
The way you used it "1 / (1 + 0) = 100%" means just "the knowledge used in the formula is that one patient died, zero recovered." In that case, yes, the fatality rate is "everybody dies." But using the sample of 1 is of course not meaningful for any statistics, not only for that formula.