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

Lucas Böttcher; Mingtao Xia; Tom Chou

After an outbreak, it is important to assess the severity of the disease by estimating its mortality and other disease characteristics. Assuming accurate data, the often-used CFR and delayed CFR typically underestimate the true, final death ratio. For example, during the SARS outbreaks in Hong Kong, the WHO first estimated the fatality rate to 2.5% (March 30, 2003) whereas the final estimates reached values of about 17.0% (June 30, 2003) [7] . Standard metrics like the CFR are seen to be easily confounded by and sensitive to uncertainty in intrinsic disease parameters . CC-BY-NC-ND 4.0 International license It is made available under a author/funder, who has granted medRxiv a license to display the preprint in perpetuity. such as the incubation period and the time Ï„ 1 a patient had been infected before clinical confirmation of infection. For the recent COVID-19 outbreaks, CFR-based measures may still provide reasonable estimates of the actual mortality across different age classes due to a counter-acting error in the numbers of unreported mild-symptom cases.