The University of Oxford’s Centre for Evidence-Based Medicine offers an extensive assessment of COVID-19 mortality and infection data in its article on Global Covid-19 Case Fatality Rates, updated daily.
“Comparison with Swine Flu
The overall case fatality rate as of 16 July 2009 (10 weeks after the first international alert) with pandemic H1N1 influenza varied from 0.1% to 5.1% depending on the country. The WHO reported in 2019 that swine flu ended up with a fatality rate of 0.02%. Evaluating CFR during a pandemic is a hazardous exercise, and high-end estimates end be treated with caution as the H1N1 pandemic highlights that original estimates were out by a factor greater than 10.
Early CFR rates are subject to selection bias as more severe cases are tested – generally those in the hospital settings or those with more severe symptoms.
Mortality in children seems to be near zero (unlike flu) which will drive down the IFR significantly.
Therefore we can estimate that the IFR is 0.29% (95% CI, 0.25% to 0.33%); at least half that of the CFR of Germany.
We could also estimate the IFR as 0.26, based on halving the lowest boundary of the CFR prediction interval. There is still considerable uncertainty over how many people actually have the disease. (Update on this issue due tomorrow 28th March).
Our assumptions, however, do not account for some exceptional cases. As in Italy, where the population is older, smoking rates, comorbidities higher, and antibiotic resistance are higher, which all can act to increase the CFR and the IFR. It is also currently not clear what the excess mortality is in this group.
It is essential to understand whether the elderly are dying with or from the disease (see the Sarah Newy report). It is also not clear if the presence of other circulating influenza illnesses acts to increase the CFR (testing for co-pathogens is not occurring), and whether certain populations (e.g., those with heart conditions) are more at risk. Understanding this issue is now critical. If, for instance, 80% of those over 80 died with the disease (20% from it) then the CFR in >80s would be near 3% as opposed to 15%. This would then lower the overall CFR (and IFR) substantially.
What matters is now is how many people get infected in a short space of time: to what extent this overwhelms healthcare services and whether they can manage. The impact of measures to reduce spread are crucial in the upward phase of a pandemic that can affect a significant number of people at any one time.”
It’s important to point out that China’s initial CFR of 17.3% (for those with symptom onset 1–10 January 2020) ultimately declined to 0.7%.1 With more comprehensive testing (and especially serologic antibody testing in random representative samples of the population), fatality rates will come down as public health officials get better estimates of the denominator. While CEBM’s IFR currently suggests that COVID-19 is 3x deadlier than seasonal influenza, data from Iceland (which so far offers the most representative data on population-level infection rates) suggests that this estimate may ultimately go down as well.
“Iceland is presenting many interesting pointers for estimating the CFR. Iceland has tested a higher proportion of people than any other country (9,768 individuals), equivalent to 26,762 per million inhabitants the highest in the world (as a comparison, South Korea has tested 6,343 individuals [per million]). The results of screenings have suggested 0.5% are infected; the true figure is likely higher due to [those who are] asymptomatic and…not seeking testing: estimates suggest the real number infected is 1%. Iceland is currently reporting two deaths in 737 patients, CFR. 0.27%; if 1% of the population (364,000) is infected, then the corresponding IFR would be 0.05%. However, they have limited infections in the elderly as their test and quarantine measures have seemingly shielded this group, and the deaths will lag by about two weeks after the infection. Iceland’s higher rates of testing, the smaller population, and their ability to ascertain all those with Sars-CoV-2 means they will likely provide an accurate estimate of the CFR and the IFR. Current data from Iceland suggests the IFR is somewhere between 0.05% and 0.14%.”
 World Health Organization. “Report of the WHO-China Joint Mission
on Coronavirus Disease 2019 (COVID-19).” 16-24 February 2020.