Condition-specific mortality risk can explain differences in COVID-19 case fatality ratios around the globe

With COVID-19 infections resulting in death according to a hierarchy of risks, with age and pre-existing health conditions enhancing disease severity, the objective of this study is to estimate the condition-specific case fatality ratio (CFR) for different subpopulations in Italy.

The design of the study was to estimate the 'pre-existing comorbidity'-conditional CFR to eventually explain the mortality risk variability reported around in different countries.

We use the available information on pre-existing health conditions identified for deceased patients 'positive with severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2)' in Italy. We (i) estimated the total number of deaths for different pre-existing health conditions categories and (ii) calculated a conditional CFR based upon the number of comorbidities before SARS-CoV-2 infection.

Our results show a 0.6% conditional CFR for a population with zero pre-existing pathology, increasing to 13.9% for a population diagnosed with one and more pre-existing health conditions.

Condition-specific mortality risks are important to be evaluated during the COVID-19 pandemic, with potential elements to explain the CFR variability around the globe. A careful postmortem examination of deceased cases to differentiate death 'caused by COVID-19' from death 'positive with SARS-CoV-2' is therefore urgently needed and will likely improve our understanding of the COVID-19 mortality risk and virus pathogenicity.