Monday, March 9, 2020

Tracking the Trajectory and Peak of Coronavirus Cases

I have seen a lot written about the Coronavirus, a.k.a. COVID-19, but I have yet to see any informed discussion about the trajectory of cases in various regions, the cycle time to peak new cases or meaningful predictions about the future course of the spread of the virus.

So here are some thoughts on the subject, using historical data from Wikipedia that is more standardized in time and collection methodology than any other data I have been able to find on the Web.  First, I examined the entire history of case data by country and found inflection points that roughly correspond to 10 new cases and 100 new cases per day.  As identification of initial cases is somewhat problematic given the variable protocols for testing, availability of testing kits, timing of nearby positive cases, etc. I elected to use the 100 new cases per day threshold.

It turns out that there have been seven countries so far that have logged 100 new COVID-19 cases in a single day.  In order of reaching that 100 new cases threshold, they are:  China (January 21st), South Korea (February 21st), Italy (February 26th), Iran (February 27th), France (March 5th), Germany (March 6th) and Spain (March 6th).  The U.S. has come close to the 100 new case threshold and may indeed hit that mark today or tomorrow.

The graphic below shows the daily number of new cases in each of the seven 100+ new case countries.  Note that it is reasonable to expect some sort of parabolic pattern for new cases with a steep jump in new cases that eventually flattens out, peaks and declines in a similar fashion.  This pattern probably would have been the case in China, except that on February 10th, China changed the methodology for counting new “confirmed” cases from relying strictly on the basis of a positive result from a lab testing kit to cases that included patients where CT scans for pneumonia allowed for a “confirmed” case clinical diagnosis for likely COVID-19 cases without having to wait for a lab test and results.

[source(s):  Wikipedia, VIX and More]

To summarize the data in the graph, three of the four countries that are at least ten days from the initial 100-case day have seen what appears to be a peak in new cases.  In China, it was 22 days from 100 cases to peak new cases, though it is possible that peak new cases might have been 14 days if China had not expanded the methodology for defining new cases to include a clinical diagnosis.

In South Korea, a concerted effort to ramp up testing as quickly as possible is probably responsible for the fact that South Korea saw a peak in new cases just 9 days after the first 100-case day.

While the peak in new case data in Iran should be considered provisional, the current peak in new cases was only 8 days after the first 100-case day, perhaps aided by the steep trajectory in new cases during the first five days.

Italy is the outlier in that there are no signs of a peak some ten days after the first 100-case day, though it is reasonable to expect that the newly implemented national lockdown and public gathering measures will help to slow the rate of new cases going forward.

The remaining three Western European countries – France, Germany and Spain are only 3-4 days into their post-100 timeline, so it is too early to talk about a peak.

The first quick takeaway is that the time from 100 new cases to peak new cases seems to cluster around 8-14 days or perhaps 8-22 days if you overlook the changes in the methodology for counting new cases in China.

Second, with the U.S. new case count hovering just below 100, it is reasonable to expect that the 8-14 day window for new cases will also apply to the U.S. putting a likely peak count in the March 17th – March 24th time frame, with an outside shot of the peak extending out to April 1st.  This assumes, of course, that the U.S. follows a similar trajectory to the other countries.  Along those lines, it will be interesting to see if Italy’s new cases peak during the next week.

Obviously, there are a number of factors that can affect how successful a country can be in containing the COVID-19 outbreak, conduct an appropriate number of tests and other factors. Japan, for instance, had its first case almost two months ago and has yet to approach 100 new cases in a day.

More to come on the COVID-19 global outbreak, the VIX, volatility and more.

Further Reading:

For those who may be interested, you can always follow me on Twitter at @VIXandMore

Disclosure(s): none

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