Covid-19 – Is it Now a Casedemic?
With the recent successful trials of vaccines for the Novel Corona Virus, the question may soon be moot, but there is a school of thought that the Covid-19 situation is now a “casedemic” rather than a pandemic. In other words, case rates are increasing with the colder weather, but this doesn’t represent the catastrophe that is generally assumed. The theory seems to come down to the following claims:
· Proposition 1: The increase in cases is misleading, since increased rates of testing are now just uncovering a lot more marginal cases, many of which are asymptomatic anyway. Besides, in most of the world it is winter and the numbers of cases of flu and related diseases always go up in the winter.
· Proposition 2: The death rate and associated “bad outcomes” are no longer that high (and are trending downwards), and they are centered in a few vulnerable grouips, so the lockdowns and other public health measures are now causing more problems than they are solving. We should just take care of the vulnerable and relax our vigilence for most of the population.
Personally, I am not strongly committed to any position. But I think it is worthwhile to test these propositions (the bolded parts) against those facts that are widely available.
Just for the record, I am a statistician/data scientist who works for a major research university, though in operational statistical analysis rather than epidemiology. Still, data is data, and any well-trained and experienced analyst can come to reasonable conclusions from the pandemic data that is publicly available.
Proposition 1: The Increase in Cases is Mainly a Function of the Increase in Testing Rates
Looking at a graph of number of test vs number of cases, by country, for the four periods in the dataset, we can see that there is a fairly strong linear relationship between tests and cases. Note that the points and lines are colour-coded for each period in the data.
Using Excel’s graphing functions and setting the regression line to have a 0 intercept, we get the following test to case ratios:
Jan 1-May8: 0.127 (12.7%)
May 9-July 5: 0.055 (5.5%)
July 6-Sept 7: 0.075 (7.5%)
Sept 8-Nov 9: 0.058 (5.8%)
We can use these as proxies for the percentage of people tested who had Covid-19. Strictly speaking, some people might be listed as Covid cases who never actually got tested, especially in the early period of the pandemic.
I realize that the graph above might not be very persuasive (is that really linear?), as a lot of the data points are squished together in the bottom left hand corner, so I did a version that uses the logarithm for both tests and cases, which shows all of the points and demonstrates the linear nature of the relationships (these relationships also have high R-squares, indicating linearity).
It seems clear that the relationship between the number of tests done and the number of cases discovered is quite linear – as the number of tests done goes up, the number of cases discovered goes up. However, the percentage of the tested who are considered Covid cases has changed over time, falling sharply since the beginning of the pandemic, from about 12% to about half that in the latter periods. However, it has been fairly stable in the last three periods, varying within in narrow band of 5.5% to 7.5%.
So, this does lend some credence to the “casedemic” argument as it shows that more testing does yield more cases. Of course, if the general level of cases was going up, it would be natural to increase the overall level of testing (i.e. call for more testing), so it isn’t clear whether more testing just uncovers more cases or more cases motivates more testing.
Proposition 2: The death rate and associated “bad outcomes” are no longer that high (and are trending downwards)
1) Death Rates
Next we can look at the number of deaths as a percentage of the number of tests. If expanded testing was locating less severe cases of Covid, we would expect that the percentage of deaths would go down over time. And that is what we see, with deaths per 10,000 cases falling from 79 to 8 over the entire period. And in this case the rate did continue to fall throughout the period, in a monotonic fashion.
Jan 1-May8: 0.0079 (79 deaths per ten thousand tests)
May 9-July 5: 0.0019 (19 deaths per ten thousand tests)
July 6-Sept 7: 0.0019 (13 deaths per ten thousand tests)
Sept 8-Nov 9: 0.0008 (8 deaths per ten thousand tests)
Again, I am presenting the logged variables graph, to show that there is a fair degree of linearity in the relationships. That is also indicated by the reasonably high R-square for each of the time periods.
This gives some support to the casedemic argument, in as much as the number of cases has risen dramatically, but the deaths have not nearly kept pace. That would indicate that greater levels of testing could be finding more cases, but those cases are less severe and therefore there have been proportionately fewer deaths as the pandemic has gone on. Thus, it could be argued that the dangerous pandemic of the late winter of 2020 has turned into a far less deadly “casedemic” in the latter part of the year.
2) Serious/Critical Rates
Of course it is possible that doctors have become better at treating the disease and other medical conditions related to the virus, bringing down the death rate, thus making the testing seem to find a lower percentage of severe cases and thereby seem less dangerous. If so, the proportion of cases that were recorded as deaths might go down, but the proportion of cases that were recorded as serious/critical should go up (i.e. serious/critical cases would replace deaths in the data, as they don’t die as often as they did, and thus transition to deaths).
The graph below shows the number of serious/critical cases compared to the number of active cases on the last day of each of the four periods (due to limitations of the data, we have to use this point-in-time measure). The evidence shows that the ratio of serious/critical cases to active cases is in fact going down over time (in a monotonic fashion), rather than increasing:
May8: 0.0226 (2.26 percent of active cases were serious/critical)
July 5: 0.0102 (1.02 percent of active cases were serious/critical)
Sept 7: 0.0063 (0.63 percent of active cases were serious/critical)
Nov 9: 0.0051 (0.51 percent of active cases were serious/critical)
Again, I am showing the same graph with log scales, to help reveal the linearity of the relationship. The rather high R-square values also indicate that the relationships are linear.
This also gives support to the casedemic
argument, in as much as the number of cases has risen dramatically, but the
serious/critical percentage of cases has not increased, but rather has
decreased. This also indicates that
higher levels of testing are finding more cases, but those cases are less
severe and therefore there have
proportionately fewer critial/serious cases as the pandemic has gone on.
Summarizing the “Casedemic” Argument
Both the death rate data and the serious/critical rate data support the argument that the dangerous pandemic of the late winter of 2020 has turned into a far less deadly pandemic in the latter part of the year – whether the term “casedemic” applies is debatable (in the dictionary sense of the term). However, it does seem to be clear that by drastically increasing testing levels, we are finding a lot more mild and asymptomatic cases, and disproportionately so. But when you stop to think about it, that is actually a positive development, rather than a negative one.
Nonetheless, the virus is still harming and killing great numbers of people. So, it makes sense to maintain a reasonable level of vigilance (e.g. social distancing, reasonable mask wearing precautions, keeping social events to small numbers, etc.), though drastic lockdowns may not be a good idea. After all, they do have harmful economic and social consequences.
This is especially so when vaccines are now on the horizon and will likely be rolled out within the next few months. Looking at things optimistically, it won’t be that long before this episode is behind us, whether pandemic or casedemic.
Sources:
KOF Swiss Economic Institute: https://kof.ethz.ch/en/forecasts-and-indicators/indicators/kof-globalisation-index.html
Worldometer Covid-19: https://www.worldometers.info/coronavirus/#countries
Some earlier Covid-19 blogs:
https://dodecahedronbooks.blogspot.com/2020/09/covid-19-continues-to-travel-around.html
https://dodecahedronbooks.blogspot.com/2020/07/has-covid-19-become-less-deadly.html
https://dodecahedronbooks.blogspot.com/2020/07/july-2020-update-covid-19-death-rates.html
https://dodecahedronbooks.blogspot.com/2020/05/covid-19-death-rates-correlate-highly.html
https://dodecahedronbooks.blogspot.com/2020/06/covid-19-impact-on-employment-no-impact.html
https://dodecahedronbooks.blogspot.com/2020/04/is-there-model-that-can-predict-when-to.html
https://dodecahedronbooks.blogspot.com/2020/03/estimating-fatality-rate-of-coronavirus.html
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And, here’s a more pleasant travel story than anticipating the worldwide journey of a virus.
A Drive Across Newfoundland
U.S.: https://www.amazon.com/dp/B07NMR9WM8
U.K.: https://www.amazon.co.uk/dp/B07NMR9WM8
Germany: https://www.amazon.de/dp/B07NMR9WM8
Japan: https://www.amazon.co.jp/dp/B07NMR9WM8
Canada: https://www.amazon.ca/dp/B07NMR9WM8
Australia: https://www.amazon.com.au/dp/B07NMR9WM8
India: https://www.amazon.in/dp/B07NMR9WM8
Newfoundland, Canada’s most easterly province, is a region that is both fascinating in its unique culture and amazing in its vistas of stark beauty. The weather is often wild, with coastal regions known for steep cliffs and crashing waves (though tranquil beaches exist too). The inland areas are primarily Precambrian shield, dominated by forests, rivers, rock formations, and abundant wildlife. The province also features some of the Earth’s most remarkable geology, notably The Tablelands, where the mantle rocks of the Earth’s interior have been exposed at the surface, permitting one to explore an almost alien landscape, an opportunity available on only a few scattered regions of the planet.
The city of St. John’s is one of Canada’s most unique urban
areas, with a population that maintains many old traditions and cultural
aspects of the British Isles. That’s true of the rest of the province, as well,
where the people are friendly and inclined to chat amiably with visitors. Plus,
they talk with amusing accents and party hard, so what’s not to like?
This account focusses on a two-week road trip in October 2007, from St. John’s
in the southeast, to L’Anse aux Meadows in the far northwest, the only known
Viking settlement in North America. It also features a day hike visit to The
Tablelands, a remarkable and majestic geological feature. Even those who don’t
normally consider themselves very interested in geology will find themselves
awe-struck by these other-worldly landscapes.
A Ride on the Kettle Valley Rail Trail: A Biking Journal Kindle Edition
by Dale Olausen(Author), Helena Puumala(Editor)
The Kettle Valley
Rail Trail is one of the longest and most scenic biking and hiking trails in
Canada. It covers a good stretch of the south-central interior of British
Columbia, about 600 kilometers of scenic countryside. British Columbia is one
of the most beautiful areas of Canada, which is itself a beautiful country,
ideal for those who appreciate natural splendour and achievable adventure in
the great outdoors.
The trail passes through a great variety of geographical and geological
regions, from mountains to valleys, along scenic lakes and rivers, to dry
near-desert condition grasslands. It often features towering canyons, spanned
by a combination of high trestle bridges and long tunnels, as it passes through
wild, unpopulated country. At other times, it remains quite low, in populated
valleys, alongside spectacular water features such as beautiful Lake Okanagan,
an area that is home to hundreds of vineyards, as well as other civilized
comforts.
The trail is a nice test of one’s physical fitness, as well as one’s wits and
adaptability, as much of it does travel through true wilderness. The views are
spectacular, the wildlife is plentiful and the people are friendly. What more
could one ask for?
What follows is a journal of two summers of adventure, biking most of the trail
in the late 1990s. It is about 33,000 words in length (2 to 3 hours reading),
and contains numerous photographs of the trail. There are also sections
containing a brief history of the trail, geology, flora and fauna, and
associated information.
After reading this account, you should have a good sense of whether the trail is right for you. If you do decide to ride the trail, it will be an experience you will never forget.
Amazon U.S.: https://www.amazon.com/dp/B01GBG8JE0
Amazon U.K.: https://www.amazon.co.uk/dp/B01GBG8JE0
Amazon Germany: https://www.amazon.de/dp/B01GBG8JE0
Amazon Canada: https://www.amazon.ca/dp/B01GBG8JE0
Amazon Australia: https://www.amazon.com.au/dp/B01GBG8JE0
On the Road with Bronco Billy
Amazon U.S.: http://www.amazon.com/gp/product/B00X2IRHSK
Amazon U.K.: http://www.amazon.co.uk/gp/product/B00X2IRHSK
Amazon Germany: http://www.amazon.de/gp/product/B00X2IRHSK
Amazon Canada: http://www.amazon.ca/gp/product/B00X2IRHSK
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