Study On The Method For Calculation Of Case Fatality Rate Based On Monitoring Big Data During A Pandemic

Objective: This study aims to develop a new method to accurately calculate the case fatality rate(CFR)while a pandemic is ongoing based on population-level monitoring big data.And then,taking the coronavirus disease-2019(COVID-19)as an example,we estimated the CFRs at the initial stage of pandemic in different countries or regions by this method,in order to provide reasonable advice and precious data for the local government and the Ministry of Public Health to evaluate the harm of infectious diseases,make relevant policies in a timely manner,and take effective measures in the early stage of the epidemic.Methods: This study developed a new method for CFR calculation while a pandemic is ongoing and termed it as T-hypothetical CFR calculation method,Thypothetical method for short,which was based on an adjusted formula: the number of deaths divided by the number of cases T days before,where T is an average delay between case confirmation and disease outcome.In this study,T was screened from a series of hypothesized values.Firstly,we explored the convergence laws by simulated growth data of cases.The laws were found that if a hypothesized T was equal to the true T,calculated real-time CFRs kept constant;If a hypothesized T was greater(or smaller)than the true T,realtime CFRs would infinitely decrease(or increase)to near the true CFR with the days went on.Thus,in the middle of many real-time CFR curves with increasing and decreasing trends calculated by arbitrarily hypothesized T values,so long as we can find the curve which was the earliest one showing the sign of levelling off,the true T value could be found and the true CFR could be obtained.As this was a new method for CFR calculation,we termed it as T-hypothetical method.Secondly,the CFRs of COVID-19 at the initial stage of pandemic in Hubei Province and non-Hubei regions of China were estimated by T-hypothetical method.True numbers of death reported officially were compared with death numbers estimated by the calculated CFR to validate the accuracy of our method.Thirdly,we applied this method for CFR estimations of other countries or regions in the world.Results: Based on the convergence laws and T-hypothetical method,it was estimated that CFR of COVID-19 at the initial stage of pandemic in China,excluding Hubei Province,was 0.8%;and in Hubei Province,it was 6.6%.The calculated CFRs predicted the death count with almost complete accuracy.European countries had higher CFRs with Netherlands 12.6%,Italy 14.1% and Belgium 18.1%;Switzerland,Poland,and Romania were approximately 6% and Ireland was 7.9%;Germany,Portugal,Austria,Norway and Czechia were lower with approximately from 3% to 4%.Out of Europe,USA was 7%,Chile was 2.1%,Israel was 1.6%.Conclusions: This study provides a new method for CFR calculation while a pandemic is ongoing using population-level monitoring data,namely T-hypothetical method.This method is not only effective and easy-to-use,but also not limited by sample size and the length of follow-up.It could be used for accurate calculation of CFRs during a pandemic instead of waiting till the end.The method could also help to provide reasonable advice and precious data for the local government and the Ministry of Public Health to evaluate the harm of infectious diseases,make relevant policies in a timely manner,and take effective measures in the early stage of the epidemic.