An epidemiological measure of the deadliness or severity of an infectious disease. The CFR is the total number of deaths divided by the total number of officially confirmed (diagnosed) cases multiplied by 100, in order to give a percentage.
There are a number of different ways to measure disease severity and the numbers can differ substantially depending on what kind of fatality ratio is being used.
With COVID-19, the most widely quoted mortality (death) measure is the CFR which changes as new data comes in. There is also a high degree of variability from country to country. The CFR can be affected by many factors including how soon cases are reported, how deaths are registered and attributed, how many tests are done (the more tests, the more mild cases are captured and the lower the CFR) and it does not account for asymptomatic cases. For these reasons, the CFR should be treated with caution. Estimates of the CFR in the early stage of the pandemic in China by province, for example, ranged from less than 1% to 5.8%
TIP: The case fatality ratio, is most commonly referred to as the case fatality rate, although strictly speaking with COVID-19, this term is incorrect because the term ‘rate’ is used to denote a time component, which is absent in the case fatality ratio. Also do not confuse case fatality ratio with mortality rate. The mortality rate refers to the number of people who die from the disease out of the total population.
Epidemiology Infectious Disease Tests