Two days after the Governor introduced a COVID-19 county risk mapping tool to try to persuade North Carolinians resistant to masks and social distancing to take precautions against viral transmission, the State topped 4,000 new COVID-19 cases in one day and set a new record-high number of hospitalizations.
Today’s N.C. Dept. of Health and Human Services dashboard reports 4,296 new COVID-19 cases in the past 24 hours and 1,538 COVID-19-related hospitalizations.
According to the NCDHHS, 38 more North Carolinians have died because of COVID-19, a number that brings the total number of deaths in the state to 4,936.
The 4,296 new COVID-19 cases are 1,000 more than were reported by the NCDHHS on Tuesday, when Governor Roy Cooper said at a briefing that, although the State’s daily case numbers are “too high,” they are only “increasing, not surging.”
The Governor has sought to distinguish North Carolina from other states currently experiencing COVID-19 outbreaks, such as the Dakotas, Iowa, Nebraska, and other heartland states, as not having a “surge” in cases. He also said that North Carolina never experienced a “spike” in cases, but rather a steady increase.
We wonder what would have to occur statewide for the Governor to consider the fast-rising number of new COVID-19 cases each day in North Carolina a surge and whether that characterization would compel him to change his strategy.
CALCULATING THE RISK OF COVID-19 IN DARE
Thanks to an astute reader’s inquiry, we went back over our recent posts regarding the Harvard Global Health Institute’s mapping of COVID-19 risk by state and county and discovered that we omitted two key words in describing the measure: per day.
The Harvard risk system calculates the number of new COVID-19 cases in a county PER DAY per 100,000 people. In contrast, the new N.C. COVID-19 County Alert System calculates the number of new COVID-19 cases in a given 14-day period per 100,000 people.
In explaining the new mapping tool Tuesday, Dr. Mandy Cohen, the Secretary of NCDHHS, cited the White House Coronavirus Task Force as the source for the metrics methodology that her department used.
You may access the COVID-19 County Alert System here: https://files.nc.gov/covid/documents/dashboard/COVID-19-County-Alert-System-Report.pdf
Is it possible for Dare County to be in Harvard’s critical red zone for reporting 30.5 new COVID-19 cases per day per 100,000 people and also in the State’s orange zone for reporting 100 to 200 new cases per 100,000 people from Nov. 1-Nov. 14, 2020?
You do the math.
Between Nov. 1-14, 2020, according to the Dare County Dept. of Health and Human Services’ dashboard, the county reported 181 new COVID-19 cases, of which 141 were local residents.
The Harvard researchers use a moving seven-day average to calculate their per-day case increase. Thus, you need to know that between Nov. 1-7, the DCDHHS dashboard reported 77 new COVID-19 cases, of which 53 were locals, and between Nov. 8-14, the numbers were 104 new COVID-19 cases, of which 88 were locals.
(Of course, the Harvard team could have used another recent seven-day period, as well.)
You also need to know that, unless there has been a radical population explosion this year, Dare County has about 40,000 year-round residents. Roughly speaking, you would have to adjust any average number of cases by multiplying by 2.5, to arrive at a per-100,000 people figure.
In the first week of November, the daily case average for the Harvard researchers is either 11, if you take into account all of the cases, or eight, if you only use the Dare County resident cases. In the next week, the numbers are 15 and 13, respectively.
Regardless of which figure you use between eight and 15 for an average, you can easily see how Harvard derived its quantification of risk of 30.5 cases per day per 100,000.
But how did the State of North Carolina calculate that Dare County had 100 to 200 new cases per 100,000 people from Nov. 1-Nov. 14, 2020?
Between those dates, as stated above, the DCDHHS reported 181 new COVID-19 cases, of which 141 were local residents. If you multiply either of those figures by 2.5, to adjust for population, you get numbers that clearly put Dare County in the red tier, which is defined as more than 200 COVID-19 cases per 100,000 people.
But here’s the rub: In order for a county to be assigned to the red tier, it also must meet one of two other thresholds, according to the NCDHHS explanation that accompanies the map. Either the county has a positivity rate of 10 percent, which Dare does not, or the impact that COVID-19 has had on the county’s hospital is “high,” which it is not.
Dare would appear to be over-qualified for the orange tier, and under-qualified for the red tier.
Obvious questions include: What population figure did the NCDHHS use for Dare County? And did it adjust for a seasonal increase of nonresidents?
This is the best we can do in deciphering the State’s determination that Dare County is in the orange tier for COVID-19 risk.
We regret any confusion that we caused by omitting the critical words “per day” in our earlier post and any confusion we may cause today with our rough figuring.
Whatever methods the NCDHHS used, we agree with Governor Cooper who said on Tuesday about the state’s COVID-19 cases: “These are numbers we cannot ignore.”
Ann G. Sjoerdsma, 11/19/20