RALEIGH, N.C. (WNCN) — Some of the coronavirus measures in North Carolina have shown incremental improvement in the nearly two weeks since the state-mandated the use of masks for people in public, a CBS17.com data analysis found.
The slight changes appear to fall in line with the results of a study published last month by healthaffairs.org that found drops in the daily growth rate of COVID-19.
The average daily growth rate on Thursday was 2.2 percent, down slightly after it was at 2.4 percent on June 26 — the day Gov. Roy Cooper’s mask mandate took effect.
It usually takes at least two weeks for the results from an event to show up in the data.
“I think it is working,” Department of Health and Human Services Secretary Dr. Mandy Cohen said Thursday. “It doesn’t mean we’re stable yet, and we have more work to do.”
To find the daily growth rate, CBS17.com used the daily cumulative case counts published by DHHS and ran them through the same formula used by the authors of the June study when they looked at 15 states, plus the District of Columbia, that required the use of masks in April and May.
CBS17.com then calculated the seven-day rolling average of those daily growth rates to account for any single-day spikes or other abnormalities.
The total number of cases has increased by 35 percent over the past 14 days — slightly better than the 38 percent increase shown during the 14 days before that.
And a projection of the effective reproduction number — or Rt, which estimates the average number of people an infected person will infect at a point in time — in the state has dropped over the past two weeks, according to a website run by a scientist from MIT.
According to data scientist Youyang Gu’s figures, the estimated Rt in North Carolina fell to 0.98 on Thursday. It was at 1.03 on June 26.
But although the percent increase is incrementally smaller, those case numbers continue to rise, with the 2,039 new cases reported Thursday the second-highest single-day total of the pandemic and just the second time the state has seen 2,000 known new cases in a day.
One argument has been that an increase in cases corresponds to an increase in testing.
Both tests and cases have increased by 35 percent over the past two weeks. But in the two weeks before the mask mandate, cases increased by a slightly higher percentage than the total test numbers did.
And with the percent of positive tests remaining fairly constant — that daily calculation has been between 8 percent and 10 percent every day since late May — it’s still roughly twice as high as Cohen and other DHHS officials want. The World Health Organization has set 5 percent positive as the standard.