Coronavirus – Wed 18 Mar 2020 – first pass at growth prediction, SARS and MERS

Posted by Kurt Eichenwald yesterday at 5:17 PM:

  • Day 1: 15 cases
  • Next 25 days: Grew to 1,000
  • Next 3 days: 2,000
  • Next 3 days: 3,000
  • Next day: 4,000
  • Next 20 hrs: 5,000
  • Next 5 hours: 6,000

To which I’ll add: 7,769 (Johns Hopkins) at 5:00 PM today. Walking backwards with the day counts he gives, the first day is 14 Feb 2020 (ikr) and those values pretty much match what can be found in other sites. The trend is, as expected, exponential:

Graph

However: I don’t know where Eichenwald got the numbers for his tweet. They somewhat match up to what Worldometers has in its chart under Total Coronavirus Cases in the United States (which is the best chart I could find from the sites that I have bookmarked). The numbers across various sites vary quite a bit, and each site provides different details.

Why ‘Exponential Growth’ Is So Scary For The COVID-19 Coronavirus in Forbes, written yesterday.

This exponential trend is anticipated to continue for at least another few weeks, even if severe social distancing actions are taken today.

from Why ‘Exponential Growth’ Is So Scary For The COVID-19 Coronavirus

If we extrapolate the data from the above graph out to just the three weeks suggested, the curve takes us to 24,000+ cases in one week, 88,000+ in two and 315,000+ cases in three (by 8 Apr 2020). That’s a month and three weeks after the date of those initial 15 cases. Current (est.) population of the US is 330,000,000 so that’s ~0.1% of the population infected by 8 Apr.

…despite the fact that the numbers of confirmed COVID-19 cases appears to be exponentially rising in the United States with a doubling time of 2.4 days, larger and longer-period studies have shown that the true doubling time is closer to 6 days, indicating that the United States data is skewed by insufficient testing.

from Why ‘Exponential Growth’ Is So Scary For The COVID-19 Coronavirus

The graphs above show a doubling time of ~4 days.

SARS and MERS

How does the coronavirus epidemic compare to SARS and MERS? in The Hill (written 24 Jan, updated 15 Mar)

It took several months for the [SARS] outbreak to be reported to the World Health Organization (WHO) on Feb. 14, 2003, when there were already more than 300 cases.

from How does the coronavirus epidemic compare to SARS and MERS?, what the hell is it with 14 Feb?!

According to the article, SARS was ~10% fatal (9.6% according to Wikipedia) and MERS 35% fatal (massive differences between age groups though, Wikipedia puts it at 11%). The fatality rate of COVID-19 is at 4% worldwide (Johns Hopkins). There is no safe and effective vaccine for SARS; none at all for MERS.

SARS has a incubation period of 2-7 days (Frequently Asked Questions About SARS). MERS starts to appear after 5-6 days, but can range from 2-14 (Middle East Respiratory Syndrome (MERS) > Symptoms & Complications). COVID-19 has an incubation period of 2-14 days, with symptoms appearing after 11.5 days (How Long Is the Incubation Period for the Coronavirus?).

Viruses that show symptoms faster and that kill their hosts faster will have a more limited spread. COVID-19’s delay and lower fatality rate may be making it more widespread.

Updated later the same night

Numbers from Mike Baker sourced from a NYT article:

  • 15 Jan: 0
  • 22 Jan: 1
  • 29 Jan: 5
  • 5 Feb: 12
  • 12 Feb: 14
  • 19 Feb: 25
  • 26 Feb: 60
  • 4 Mar: 160
  • 11 Mar: 1,262
  • 18 Mar: 8,264

The curve is sharper (lower earlier, higher later) than from my graph.

Ryan Struyk:

  • 1 Mar: 89
  • 2 Mar: 105
  • 3 Mar: 125
  • 4 Mar: 159
  • 5 Mar: 227
  • 6 Mar: 331
  • 7 Mar: 444
  • 8 Mar: 564
  • 9 Mar: 728
  • 10 Mar: 1,000
  • 11 Mar: 1,267
  • 12 Mar: 1,645
  • 13 Mar: 2,204
  • 14 Mar: 2,826
  • 15 Mar: 3,505
  • 16 Mar: 4,466
  • 17 Mar: 6,135
  • 18 Mar: 8,760

And finally: The 7,769 cases at 5 PM today has changed to 9,345 at midnight. A 20% increase in 7 hours.