Why estimating population-based case fatality rates during epidemics may be misleading

Lucas Böttcher; Mingtao Xia; Tom Chou

Here, we stress that more mechanistically meaningful and interpretable metrics can be defined and be as easily estimated from data as CFRs. Our proposed mortality ratios for viral epidemics are defined in terms of (i) individual survival probabilities and (ii) population ratios using numbers of deaths and recovered individuals. Both of these measures are based on the within-host evolution of the disease, and in the case of M 0,1 p (t), the population-level transmission dynamics. Thus, these metrics directly incorporate key parameters operating on the weeks or months timescale, the incubation time τ inc and time of prior infection τ , through the solution of age-structured PDEs. Among the metrics we describe, M 1 p (t) is structurally closest toM 1 (t) in that both are independent of transmission β since new infections are not considered. Both of these converge after an incubation time τ inc to a value smaller than or equal to µ 1 /(µ 1 + c).