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--- blog:2020-03-22:covid-19_spread_part_ii [2020/04/12 12:55] – va7fi
+++ blog:2020-03-22:covid-19_spread_part_ii [2020/08/07 13:03] (current) – external edit 127.0.0.1
@@ Line 1: / Line 1: @@
-====== COVID-19 Spread (Part II) ======
+====== COVID-19 Spread (Part II) Updated ======
 <WRAP center round important 90%>
   * I'm not an epidemiologist, doctor, or any kind of expert on the subject.  I just look at the numbers.
   * This was originally written on Sunday March 22nd.
-  * Jump straight to the [[#april_12th_update |latest update]]
 </WRAP>
+<WRAP center round tip 90%>
+  * Jump straight to the [[#april_17th_update |latest update]].
+</WRAP>
@@ Line 135: / Line 139: @@
 |<100% >|
 |  <fc #4682b4>Logistic 1</fc>  |  <fc #800000>Logistic 2</fc>  |  <fc #008000>Logistic 3</fc>  |
-|  $$N = \frac{2660}{1 + e^{-0.32(t - 21.1)}}$$  |  $$N = \frac{12000}{1 + e^{-0.232(t - 30)}}$$  |  $$N = \frac{20000}{1 + e^{-0.24(t - 32)}}$$  |
+|  \$$N = \frac{2660}{1 + e^{-0.32(t - 21.1)}}\$$  |  \$$N = \frac{12000}{1 + e^{-0.232(t - 30)}}\$$  |  \$$N = \frac{20000}{1 + e^{-0.24(t - 32)}}\$$  |
 </hidden>
 \\
@@ Line 255: / Line 259: @@
 <WRAP indent>Why is it that back in [[blog/2020-03-16/covid-19_spread |March]], I seemed to trust the numbers when they said that the virus was spreading exponentially, but now I seem to distrust the numbers when they say that the infection rate is finally levelling off?  Am I just a pessimist regardless of what the evidence says?</WRAP>
-The quick answer is no.  The way evidence works is not symmetrical.  Imagine you think there might be a mouse in the basement so you set a mouse trap:
+The quick answer is no.  The way evidence works is not symmetrical.  For example: imagine you think you might have mice in the basement, so you setup a few traps:
-  * If you catch it, you can, with 100% certainty, say that there was (at least) one mouse.
+  * If you catch a mouse, you can, with 100% certainty, say that there was (at least) one mouse in the basement.
   * If you don't catch anything, you can't say anything with 100% certainty.  Maybe there isn't one, but maybe there is and you just didn't catch it.
 So back in March, the reported cases grew exponentially, so I could say with 100% certainty that the virus was spreading exponentially (although maybe at a faster rate than reported).  Now, the reported cases seem to be growing linearly (the curve is flattening).  But there are two possible explanations for this:
   - The infection is actually flattening out (I really hope and wish this is the case), or
-  - The amount of testing we do is insufficient and we are not recording the actual spread of the virus (I suspect this is the case).
+  - The amount of testing we do is insufficient and we are not recording the actual spread of the virus (this might very well be the case).
 It's hard to say exactly which of these it is because the provinces aren't releasing the daily number of tests they perform (or if they do, I haven't found them anywhere).  But there is some evidence pointing to a lack of testing.  One of them is if we compare the number of deaths for each provinces relative to the number of cases reported.  Here are the numbers from yesterday for BC, Alberta, Ontario, and Quebec:
-^Province	^Cases	^Death	^Death Rate |
+^Province	^Cases	^Deaths	^Death Rate |
 ^BC	|1445	|58	|4.0%|
 ^AB	|1569	|40	|2.5%|
@@ Line 273: / Line 277: @@
 The number of cases and the number of deaths are reported daily.  The Death Rate is a calculation:
 <WRAP centeralign>
-$$\text{Death Rate} = \frac{\text{\# of Deaths}}{\text{\# of Reported Cases}}$$
+\text{Death Rate} = \frac{\text{\# of Deaths}}{\text{\# of Reported Cases}}
 </WRAP>
 Another way to think of this is: for every 100 reported cases, how many people die?
-From this, we see that BC has 4 deaths per 100 reported cases, where as Quebec has 2.4 deaths per 100 reported cases. This suggests that there are a lot more unreported cases in BC since the death rates should be relatively similar across the country.
+From this, we see that BC has 4 deaths per 100 reported cases, where as Alberta has 2.5 deaths per 100 reported cases. This suggests that there are a lot more unreported cases in BC since the death rates should be relatively similar across the country.
 What we hear from the news also supports this: Alberta is being praised for the high number of tests they are performing (and their death rate is low) while Ontario is being criticized for the opposite (and their death rate is high).
@@ Line 314: / Line 318: @@
 Unfortunately, Dr. Henry doesn't seem to think that it's a problem: [[https://www.cbc.ca/news/canada/british-columbia/reports-of-crowded-ferries-overblown-most-people-staying-home-b-c-health-officer-1.5530117 |Reports of crowded ferries 'overblown']].
+===== April 17th Update =====
+I finally found a key piece of data((The site I have been using just added the number of tests performed recently: [[https://www.covid-19canada.com/]])) that I had been missing since the beginning: the number of tests performed by different provinces.
+Here's a summary of the four most populous provinces as of the end of yesterday:
+^Province ^Tests ^Cases ^Deaths ^Population (Millions) ^^Cases / Tests ^Death / Cases ^Tests / Million ^Cases / Million ^Death / Million |
+^BC |59185 |1575 |77 |5.111 ^|2.7% |4.9% |11580 |308 |15 |
+^AB |85502 |2158 |50 |4.413 ^|2.5% |2.3% |19375 |489 |11 |
+^ON |128093 |8961 |423 |14.712 ^|7.0% |4.7% |8707 |609 |29 |
+^QC |151510 |15857 |630 |8.538 ^|10.5% |4.0% |17745 |1857 |74 |
+That's a lot of numbers so let's unpack this table a bit:
+  * The "Tests", "Cases", "Deaths", and "Population" columns are raw data.
+  * The other columns are calculations:
+    * "Cases / Tests" is the percentage of tests that come back positive.
+    * "Death / Cases" is the number of death for every 100 **reported** cases.
+    * "Tests / Million" is the number of tests performed per million people in each province.
+    * "Cases / Million" is the number of reported cases per million people in each province.
+    * "Deaths / Million" is the number of deaths per million people in each province.
+So let's compare these four provinces.
+==== Number of Reported Cases ====
+If we look at the total number of reported cases, it looks like BC is doing the best and Quebec is the worst:
+  * BC: 1575 cases
+  * AB: 2158 cases
+  * ON: 128093 cases
+  * QC: 151510 cases
+If we take these numbers and scale them to take account of each provinces' population, the rank is still the same (although we can see that Quebec is doing three times worse than Ontario):
+  * BC: 308 cases / million
+  * AB: 489 cases / million
+  * ON: 609 cases / million
+  * QC: 1857 cases / million
+It would be tempting to stop there, but the problem is that not every province is testing the same.  This means that some provinces might have a more realistic view of the infection rate than others.
+==== Death Rate ====
+The first clue to this is to look at the number of deaths per hundred cases:
+  * AB: 2.3 deaths per 100 reported cases.
+  * QC: 4.0 deaths per 100 reported cases.
+  * ON: 4.7 deaths per 100 reported cases.
+  * BC: 4.9 deaths per 100 reported cases.
+This time, the ranking is very different as BC went from being first to being last.  There are a few different things that could explain this:
+  * Maybe in Quebec, Ontario, and BC, it's the most vulnerable population that contracted the virus, leading to more deaths.
+  * Maybe Alberta has unusually successful treatments for people infected.
+  * Maybe different provinces are not reporting their infected cases in the same way.
+We would expect some variation, of course, but for BC to be #1 when it comes to having the fewer number of cases, and then the worst when it comes to the number of deaths / reported cases suggests that we are under-reporting.
+==== Number of Tests ====
+After over a month of looking at these numbers, we finally got access to the number of tests being performed.  If we look at the number of tests / million people, we get the following ranking (the higher the better):
+  * AB 19375 tests / million
+  * QC 17745 tests / million
+  * BC 11580 tests / million
+  * ON 8707 tests / million
+Unsurprisingly, Alberta is the best, closely followed by Quebec(!) and trailing behind is BC and Ontario.
+Per capita, Alberta has tested 1.7 times more than we have so far.  So it would be reasonable to estimate that if we had tested 1.7 times more, we could have found 1.7 times more cases, which would have brought our total from 1600 cases to 2600 instead.  This would in turn have lowered our death rate from 4.9% to 2.9%, which is closer to Alberta's 2.3%.
+==== Positive Result Rate ====
+Another number that is very interesting to look at is the number of positive cases per 100 tests performed.  Here, it's not obvious what's good:
+  * A low number could mean that we are testing uninfected people just to make sure (health care workers for example).  But it could also mean that we are sending infected people home to self isolate without testing them (the way BC has been doing it for weeks now).
+  * A high number could mean that we are testing people that are more obviously infected.  But it could also mean that we are not testing enough people "just to make sure".
+At any rate, There's a clear divide between the west and the east here and I'm not sure what to make of it.
+  * AB:	2.5%
+  * BC:	2.7%
+  * ON:	7.0%
+  * QC:	10.5%
+==== Conclusion ====
+One of the main conclusions from this is that, as suspected, BC is behind on testing (and Ontario is worse) and until we start ramping up on testing, we just can't judge how good (or bad) the situation is.  Any future changes to the current physical distancing measures will be made in the dark.