This question is much more relevant, but less straightforward to answer.
Reports of the virus’s lethality vary by an order of magnitude.
On March 3 the World Health Organization stated the death rate was 3.4%. Other widely quoted estimates have put the figure at 3% or 5%. But other sources have estimated it at well under 1%.
One reason for these discrepancies is that they often use two different ways to calculate the death rate.
The Case Fatality Rate (CFR) is the number of deaths divided by the number of known infections. This figure can be greatly biased upwards or downwards due to sampling.
Imagine the virus infects 100 people; 70 are asymptomatic and unaware of their infection, while 30 fall sick and are diagnosed, and 1 of these 30 people dies.
In this example the true death rate is 1% (1/100), but the CFR is 3.3% (1/30).
This bias is often strongest during an outbreak’s early stages, when many mild cases are missed and the number of confirmed cases is still low.
For this reason, some epidemiologists now think the initially reported death rates are severe overestimates.
There is a second measure we can use here, which corresponds more closely to most people’s idea of “deadliness”. The Infection Fatality Rate (IFR) is the number of deaths divided by the true number of infections (including both confirmed and undiagnosed cases). This statistic is harder to calculate, as it requires estimating the number of undetected infections.
One estimate of the IFR for COVID-19 puts this figure at 1%, and some new data suggests this is credible.
As testing becomes more rigorous, the discrepancy between the two measures (CFR and IFR) gets smaller. This may be happening in South Korea, where exhaustive testing has detected many mild infections and pushed the estimated death rate down to 0.65%.
Similarly, the stricken cruise ship Diamond Princess is illuminating because the rigorous quarantine meant nearly all COVID-19 cases (even asymptomatic ones) were identified. There were 7 deaths among more than 600 infections, giving an IFR of about 1.2%. This is higher than in South Korea, but perhaps expectedly so, given that one-third of the ship’s passengers were aged over 70.
Because the virus hits old people hardest, countries with ageing populations will be more severely affected. Based purely on demographics, the projected death rate in Italy is seven times the rate in Niger; Australia is worse than the global average. Of course, the eventual death rates will also depend on countries’ health systems and containment responses.
This age-selective mortality of COVID-19 should be explicitly considered in plans to combat it. In Australia, 11% of the population are over 70 and are predicted to account for 63% of deaths. Insulating a relatively small proportion of elderly people will halve deaths and is potentially more practical than total lockdown of entire populations. We need to urgently focus on the best way to achieve this. At the time of writing, the UK is seriously discussing this strategy.
http://theconversation.com/the-coronavi ... flu-133526
Why 3.4% is likely an overestimate
Dr. Toni Ho, a consultant in infectious diseases at the Medical Research Council (MRC)–University of Glasgow Centre for Virus Research, U.K., echoes similar sentiments.
She goes on to suggest that the figure of 3.4% is likely an exaggeration, mainly due to the challenges of calculating mortality rates outlined above.
“The quoted mortality rate of 3.4% is taken from confirmed deaths over total reported cases. This is likely an overestimate, as a number of countries, such as the United States (112 confirmed, 10 deaths) and Iran (2,336 cases, 77 deaths), have had limited testing. Hence, few of the mild cases have been picked up, and [the total number of cases] we are observing is the tip of the iceberg.”
In fact, the overestimation could be 10 times higher than the reality, notes Mark Woolhouse, a professor of infectious disease epidemiology at the University of Edinburgh, U.K.
“[I]f a significant number of mild cases have been missed or not reported, then this [3.4%] estimate is too high.”
“Though there is disagreement about this, some studies have suggested that it is approximately 10 times too high. This would bring the death rate in line with some strains of influenza.”
– Prof. Mark Woolhouse
https://www.medicalnewstoday.com/articl ... er-factors