My assumptions are pretty straight forward, the infection rate for the flu is generally known, but that's with both vaccination and herd immunity - without those two, a highly infectious virus will cover the majority of the population in a few months if no measures are taken to reduce the rate of infection, especially when many are asymptomatic while infectious.
As far as death rates, again, we have data on the flu, and it seems to vary between .06% and 0.13%, depending on the strain.
We won't know what the mortality rate for COVID is until we have widespread testing, but the initial estimates of 3% seemed way too high (denominator was too small), but there's still a lot of uncertainty.
Lot of different estimates for Infected Mortality Rates (IFR):
[note the Italian deaths seem to be overstated, they assume everyone who died with COVID were killed by COVID]
Neil Ferguson’s team at Imperial College, London, Their Infection Fatality Rate estimates were based on
from Verity et al. and adjusted to account for a non-uniform attack rate giving an overall IFR of
0.9%
Verity et al., Estimates of the Severity of COVID 19 Disease
Estimates of the severity of COVID-19 disease
Findings: We estimate the
mean duration from onset-of-symptoms to death to be 17.8 days (95% credible interval, crI 16.9,19.2 days) and from onset-of-symptoms to hospital discharge to be 22.6 days (95% crI 21.1,24.4 days). We estimate a crude CFR of 3.67% (95% crI 3.56%,3.80%) in cases from mainland China. Adjusting for demography and under-ascertainment of milder cases in Wuhan relative to the rest of China, we obtain a best estimate of the CFR in China of 1.38% (95% crI 1.23%,1.53%) with substantially higher values in older ages. Our estimate of the CFR from international cases stratified by age (under 60 or 60 and above) are consistent with these estimates from China. We obtain an overall
IFR estimate for China of 0.66% (0.39%,1.33%), again with an increasing profile with age. Interpretation: These early estimates give an indication of the fatality ratio across the spectrum of COVID-19 disease and demonstrate a strong age-gradient in risk.
Diamond Princess: IFR
0.5%
Our current best assumption, as of the 22nd March, is the IFR is approximate
0.20% (95% CI, 0.17 to 0.25).
Therefore, to estimate the IFR, we used the estimate from Germany’s current data 22nd March (93 deaths 23129) cases); CFR 0.51% (95% CI, 0.44% to 0.59%) and halved this for the IFR of
0.26% (95% CI, 0.22% to 0.28%) based on the assumption that half the cases go undetected by testing and none of this group dies.
Current data from Iceland suggests the IFR is somewhere between
0.05% and
0.14%. But Iceland protected their most vulnerable citizens.
Global Covid-19 Case Fatality Rates - CEBM
