The Personal Blog of Stephen Sekula

Hot Spot (C+85)

Redfield was then asked for a definition of “hot spots.” He said it would include places where more than 5 percent of coronavirus tests come back positive. Looking county by county, he said “the majority of the nation” is not a hot spot.

“CDC director concedes schools in ‘hot spots’ face tougher call on reopening”. The Washington Post. July 25, 2020.

If you look at the numbers in Collin County – the number of new coronavirus cases per day – you might be convinced that something good is happening. Back on about day 128 after the county started reporting COVID-19 data, we hit the single-day high of new cases. We had just over 200 new cases of COVID-19 in a single day. This came around the average peak daily new cases.

Since day 128, we’ve dropped a little in the new cases count; at worst, we’ve remained generally level. You might be tempted to think things are better.

In reality, it’s not that simple. The case counts are dropping because the amount of testing for COVID-19 has declined. Just as case counts gently dropped off, so did the total number of COVID-19 tests. But something stayed constant: the rate of positive tests.

Collin County did not report test positivity rates until about 50 days after they started collecting and reporting local data on the pandemic. Of course the rates were high at the beginning; tests were available primarily to people showing signs of illness. When testing became more widespread, we began to better sample the “true positive” rate. During that era or more widespread testing, the positivity rate was around 16%.

While the CDC’s advice may have recently been compromised by the President, some clear and honest truths still slip out. Redfield understands a “hot spot” to be a place with a >5% positivity rate. Like all the counties across the DFW metroplex, we are a hot spot.