New COVID-19 cases in Pima County are on an uneven downslope.

Meanwhile, the downslope of new COVID-19 cases across Arizona has been smoother. Most counties in Arizona have seen a relatively consistent decrease in new COVID-19 cases from week to week since peaking in late June.

“In general, Pima County is worrying me a little bit,” said Dr. Joe Gerald, an associate professor with the University of Arizona’s Zuckerman College of Public Health. “When we look at Pima County, there’s a flattening that occurs in August.”

Some of this can be explained by one-off events, like an outbreak at a Tucson prison unit that the Arizona Department of Corrections announced on Aug. 4.

Even so, the background trend in new cases is concerning, Gerald said, pointing out that this trend is behaving differently than in other places in the state.

In Pima County, the total number of weekly cases has dropped, then risen, then dropped again since early July.

Now the number of weekly cases is rising again, from the first week in August to the second, according to the Arizona Department of Health Services’ chart of COVID-19 cases by date as of Friday.

So far, cases haven’t risen by much this time, just by 106, or 13%, from Aug. 2-8 to Aug. 9-15. And the number of diagnostic tests has risen by about 9% at the same time.

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Both these numbers, the weekly test and case totals, will very likely increase over the next week as more diagnostic tests from Aug. 9-15 are reported.

The week before, new cases in Pima County totaled 832 from Aug. 2-8. This was a decrease of 687 cases, or 45%, from the week of July 26 to Aug. 1.

At the same time, diagnostic tests remained relatively flat countywide, decreasing by 5%.

“If you look into Pima County, we are continuing to sustain a really high level of testing,” said Dr. Francisco Garcia, Pima County’s chief medical officer. “What you’re seeing is the impact of when we’re really aggressive about testing. We are going to find more disease.”

Over the last three weeks, for example, Pima County has tested for COVID-19 at a higher rate than Maricopa County. Pima County has conducted 815 to 888 tests per 100,000 people, while Maricopa county has conducted 674 to 749 tests per 100,000 people.

Gerald gives less weight to the idea that testing explains Pima County’s case trends. He hasn’t come up with a satisfactory explanation, he said, adding. “It does have me a bit concerned.”

Unlike Pima County, the curve of COVID-19 cases in Arizona has been a “nice, relatively symmetrical up-and-down peak,” Gerald said, adding that he’s paying more attention to Pima County because it’s not behaving like the rest of the state.

Since the beginning of July, the number of new COVID-19 cases each week has decreased by 24% to 36% across the state, according to ADHS’s chart of COVID-19 cases by date as of Friday.

Statewide, new cases totaled 5,874 from Aug. 2-8. This was a decrease of 33% compared with the previous week. At the same time, diagnostic tests remained relatively flat, decreasing by about 7%.

Despite a downward trend of cases throughout the state, The risk of COVID-19 remains elevated.

The Harvard Global Health Institute’s risk-level map gave Arizona an “orange” rating as of Friday, which is the second highest of four categories: green, yellow, orange and red. It means communities are experiencing “accelerated spread.”

Pima County was also rated “orange.”

The color categories are based on the seven-day moving average of new daily cases per 100,000 people.

“As long as there’s this relatively high level of background transmission within the community, we still need to be vigilant in our individual behaviors so that we can protect everybody else in the community and prevent a third wave or resurgence (of cases),” Gerald said. “So I think we’re going to be wearing masks for at least another year.”

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Contact reporter Alex Devoid at adevoid@tucson.com or 573-4417.

On Twitter: @DevoidAlex

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