Let there be a sample of 10,000 people.
100 of them have a fever. You test them for COVID19 and they all come out positive. 5 of them die, 9 of them end up in intensive care. The estimated mortality is 5%, and estimated intensive care rate is 9%. What about the 9,900 asymptomatic people who did no get tested?
Scenario A: All 9,900 asymptomatic people would test negative for COVID19. Scenario B: All 9,900 asymptomatic people would test positive for COVID19 because of a combination of high rate of asymptomatic carriers and high false positive rate. End result:
Scenario A: true mortality rate is 5% and true intensive care rate is 9%. Scenario B: true mortality rate is 0.05% and true intensive care rate is 0.09%. the numbers are fictitious, but the point is simple - we can't estimate mortality without knowing the prevalence
Where are we right now between scenario A and scenario B? Or put another way, are there any ongoing studies/reports which take into account this factor?