|Ora et Labora. Life goes on.|
I like to follow statistics. For new readers I have taken doctoral levels courses in statistics, so I know a little bit about them, and how to read them. Data informs statistics and the more data we have, the more reliable statistics become.
We need to be concerned, vigilant, and proactive. But this is NOT the Black Death.
The key to understanding the trajectory of the coronavirus is to study reliable data coming from countries such as Italy and Germany.
It is important to consider the influence of pre-existing conditions and comorbidities. (I should note that this morning I heard that obesity has just been very recently added as a known comorbidity). As with any coronavirus, the state of each person's immune system is also factor; those who are asymptomatic or develop only very minor symptoms.
The following is data released March 20, 2020 from Italy based on 481/3200 dying patients:
Mean number of diseases 2.7 (media 2, SD (Standard Deviation) 1.6)
0 comorbidities: 1.2%
1 comorbidity 23.5%
2 comorbidites 26.6%
3 + comorbidities 48.6%
So how many may die? That is the question. The Infection Fatality Rate (IFR) is the way to calculate it.
The IFR is extremely important and differs from the Case Fatality Rate (CFR). The former reflects a calculation on ALL those who have been detected and undetected (including a substantial number who are asymptomatic). Based on calculations from Germany we have the following results for fatality amongst those infected:
Therefore, to estimate the IFR, we used the estimate from Germany’s current data 22nd March (93 deaths 23129) cases); CFR 0.40% (95% CI, 0.33% to 0.49%) and halved this for the IFR of 0.20% (95% CI, 0.17% to 0.25%) based on the assumption that half the cases go undetected by testing and none of this group dies.
We can now use the German number to calculate a approximate IFR for Canada and the USA, IF rigorous social distancing is undertaken, and IF we have increased proactive testing, surveillance, and strict regional zone lockdowns (e.g. NO one is allowed to leave NYC). Otherwise hotspots will keep breaking out.
I have read estimates that in the United States 150 million will be at one time infected. I am going to increase that to 200 million (60%). For Canada it equals 22.8 million. For Britain it is 39 million.
The IFR for the USA is: 400,000
The IFR for Canada is: 45,600
The IFR for the United Kingdom : 78,000
The BAD news is that given the lack of data, the above EXCLUDES those who have a comorbidity. The "good" news is that with experimentation with antivirals, prophylactic interventions, and potential vaccines coming next year, the numbers will come down.
The first wave we are presently seeing is the worst since there were no measures in place to mitigate transmission. We now know that coronavirus was being widely spread in January all over Europe and North America. Based on this it is has been estimated that at least 50% of the population may be asymptomatic. After the initial lockdown which should flatten the curve, medical services and supplies can then be freed up to care for a steady stream but more predictable stream of sick patients.
Late April, early May (at the very latest) will be the time for us to get back to work, to life. Measures should be in place by then to protect the vulnerable. Those persons who are in the above categories will have to make serious changes in their lives.