COVID-19 Case Fatality Rate: Misapprehended Calculations

Coronavirus disease 2019 (COVID-19) pandemic, posed by sever acute respiratory syndrome coronavirus – 2 (SARS-CoV-2), is killing tens of thousands of people globally. It is disrupting societies and economies across the globe with widespread uncertainty. As of August 10, 2020, the total cases of COVID-19 have risen above 20 million and death tolls to nearly 0.74 million1 with the case fatality rate (CFR) of 3.651. The CFR indicates proportion of persons who die from a specified disease out of all individuals diagnosed positive over a specific period. Thus, the CFR is based on the number of deaths and confirmed cases. However, number of confirmed cases is not including asymptomatic cases or patients with mild symptoms, which in turn may not get tested and may not reflect the actual CFR. CFR is also proportionately variable depending on the level of testing done in a population or a country. When testing is done very extensively covering large population including symptomatic patients and non-symptomatic contacts, the denominator of the CFR calculation increases which will reduce the CFR compared to limited testing carried out only on symptomatic patients. Huge variation in the CFR was observed between different countries. The CFR in early stage of the epidemic was 0.15% (95% CI: 0.12-0.18%) in China excluding Hubei and 1.41% (95% CI: 1.38-1.45%) in Hubei province excluding Wuhan city, and it was 5.25% (95% CI: 4.98-5.51%) in Wuhan2named COVID-19, hit a major city of China, Wuhan in December 2019 and subsequently spread to other provinces/regions of China and overseas. Several studies have been done to estimate the basic reproduction number in the early phase of this outbreak, yet there are no reliable estimates of case fatality rate (CFR. The CFR rate of was found very high among countries such as France, Italy, Spain and USA viz., 13.7%, 13.5%,10.2%, and 5.7%, respectively3. Fig. 1 shows CFR of world and selected countries as of 22nd July 2020. It highlights the differences among countries while noting changes in the protocols of testing (www.ourworlddata.org/coronvirus).