Investigating spatial variability in COVID-19 pandemic severity across 19 geographic areas, Spain, 2020

Sushma Dahal; Kenji Mizumoto; Gerardo Chowell

The case fatality ratio is a useful metric to assess pandemic severity, which is typically estimated as the proportion of deaths among the total number of cases attributed to the disease [2] . However, during the course of outbreak of an infectious disease outbreak such as COVID-19, real-time estimates of CFR need to be derived carefully since it is prone to ascertainment bias and right censoring [2, 3] . In particular, the disease spectrum for COVID-19 ranges from asymptomatic and mild infections to severe cases that require hospitalization and specialized supportive care. This may lead to overestimation of the CFR among ascertained cases. On the other hand, there is a delay from illness onset to death for severe cases [4] , which could lead to an underestimation of the CFR [3, 5] . Therefore, statistical methods that help mitigate inherent biases in estimates of the CFR should be employed to accurately plan for medical resources such as ICU units and ventilators, which are essential resources to save the lives of critically ill patients [6] [7] [8] .