Can judgments according to case fatality rate be correct all the time during epidemics? Estimated cases based on CFR in different scenarios and some lessons from early case fatality rate of coronavirus disease 2019 in Iran

The new Coronavirus disease (COVID-19) was first identified in China in 2019. Case fatality rate (CFR) indicator of the disease is one of the most important indices noticed by experts, policymakers, and managers, based on which daily evaluations and many judgments are made. CFR can change during epidemics. This study aimed to estimate the actual number of COVID-19 cases in Iran and to calculate the early CFR for the disease based on official statistics.

This was a descriptive study whose data were obtained from the website of the Ministry of Health and Medical Education of Iran from February 20, 2020 until March 26, 2020. CFR has been obtained by dividing the total number of deaths by the total number of confirmed cases at one point in time. In this study, the actual number of COVID-19 cases in Iran was estimated based on the mortality model in 4 scenarios. Excel 2013 software was used to analyze the data.

According to the findings of this study, In Iran, until March 26, 2020, a total of 27 017 people have been infected by COVID-19 and 2077 died of it. However, CFR indicator had a descending trend in Iran: 100%, 18.6%, 8.8%, 3.3%, 6.9%, and 7.7% on days 1, 5, 10, 20, 30, and 35, respectively. The actual number of COVID-19 cases in Iran was estimated to be 4 789 454, 2 873 673, 1 436 836, and 718418 as of March 26, 2020 according to the 4 scenarios, respectively.

In emerging epidemics, CFR indicator must not be used as a basis to judge the performance of a health system unless that epidemic condition has been clarified. Moreover, it is suggested that in the outbreak of an epidemic, specifically emerging diseases, CFR must not be the base of judgment. Making judgments, specifically in the outbreak of emerging epidemics, based on fatality rate can lead to information bias. It is also possible to estimate the total number of patients based on the CFR in circumstances where little information is available on the disease.