The problem is we do not know how many people get sick for every 100 people who are exposed to the virus, because there can be several unreported assymptomatic antigen-positive people. So we do not know the exact death rate.
Case Fatality Rate = Number of deaths/Confirmed cases. Most initial studies have shown this rate to be around 2% to 4%. This was the rate that initiated the global chaos. This does not include the people who have got infected but did not get tested or people who got tested but did not report or the people who were just asymptomatic.
Infected Fatality Rate = Number of deaths/All infected (tested and untested). This does not include people who have been directly exposed to the virus but did not get infected (asymptomatic).
Some use Infection Fatality Rate = Number of deaths/All infections (including asymptomatic, positives tested and untested)
Exposure Fatality Rate = Number of deaths/Everyone who got exposed to the virus in close contact in the area of the study. Not everyone who is exposed to the virus will by symptomatic. That is why it is difficult to calculate the exact fatality rate of the virus when we do not know how many people who got exposed to the virus in close contact will be asymptomatic and how many of them will be positive for antigens or antibodies.
Global Fatality Rate = Number of deaths/Everyone in the world during the time period of interest.
This is why it is important to present the information properly and understand which population is included in the denominator.
All the population can be categorized into the below groups:
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