- On the other hand, an error that leads to an underestimation of the CFR is that every case is counted from the time of diagnosis, but at this point it is not yet clear whether the patient will survive. The cumulative deaths would therefore have to be compared with the number of known illnesses at the time at which the disease first manifested itself in the deceased, i.e. the number of illnesses about 14 days before the date of death, assuming that those affected die on average two weeks after illness onset. The CFR would then range between 5 and 15% depending on the country [7].