Racing toward 25%

Friday (tomorrow) is the day that Texas’s Governor allows all businesses to reopen, but only if they cap their in-house customers at 25% of capacity for their facility. So where is my county, Collin County, right now?

Anticipating this “momentous” day of continuing to re-open businesses in Texas, Collin County is stalled in its fight against the spread of SARS-CoV-2.

Data for Collin County, TX. (PINK SOLID) The number of new cases per day, averaged over the previous 7 days. (PURPLE DASHED) The number of new cases reported on a given day. (BLUE ARROWS) Key events in Texas regarding policy and COVID-19. (BLACK NUMBERS) The doubling rate of new cases, computed by fitting an exponential growth function to the prior 7 days of data.

Early on in the pandemic, Collin County achieved a 2-day doubling time for new cases. This is nothing to be proud of; the shorter the doubling rate, the faster the deadly disease spreads. Those early numbers and their rise is due to two effects: the spread of the virus, and the ramp-up of disease testing capability (when you look, you always find the cases that were already there in plain sight).

We peaked in new reported COVID-19 cases per day about 35 days after the first reported case in Collin County. It was around that time that the shelter-in-place orders put into effect between days 19-26 after first-reported-infection kicked in. We came down fast. Rather than doubling every 9 days (our rate when we hit the peak number of new cases per day) we fell to a low of about 10 new cases per day and a doubling rate of 35 days.

That was the best we did. Coincidence or not, about 15 days after the CDC recommended everyone wear a face covering (note that they recommended a covering, independent of its ability to stop infection), we bounced. New infections each day began to climb again, and our new-case doubling rate worsened to every 20 days. We’ve wobbled there now for days.

The Governor allowed all businesses to reopen for delivery or pickup about 6 days ago. Tomorrow, Texas businesses can accept people into their establishment so long as not more than 25% of capacity is utilized and social distancing is observed.

But in Collin County, TX, we are not seeing declining infection rates. We are hovering. And opening up more, now, will only lead to more spread of the virus.


The plot is made using data from the Texas Department of Health. Collin County reported cases are updated daily by about noon, US Central Time. The actual figure is made using Python, specifically:

  • MatPlotLib: graphical representation of data
  • Pandas: data storage and analysis, including averaging over sequential days
  • SciPy: curve fitting an exponential growth function to ranges of data
  • Seaborn: high-quality time-series plotting

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