Wastewater being used to estimate BA-5 cases in Pima County

KOLD News 6-6:30 p.m. recurring
Published: Jul. 20, 2022 at 6:46 PM MST
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TUCSON, Ariz. (KOLD News 13) - It’s clear now that the BA-5 coronavirus variant is dominate in Pima County, now making up 80% of the new cases.

But how many cases remains unclear.

“In the last couple of weeks there’s been an uptick,” said Ian Pepper, an epidemiologist at the University of Arizona who uses wastewater to track COVID. “The number of infections is increasing somewhat as we speak.”

The reason he knows that is he studies the wastewater of 350,000 Tucson customers. It’s called wastewater epidemiology.

Without getting too technical, Pepper studies the wastewater to determine how many COVID cases there are. Feces can tell him a lot.

“Clinical testing cannot be mandated,” Pepper said. “So at times, the wastewater is the only indication of what’s going on with COVID.”

And what the wastewater shows and what the state data dashboard shows are not the same thing.

For Pima County, the data shows 2,251 new cases last week but most believe that’s a low ball.

“Many have asymptomatic illness, many have very few or minor symptoms, some just really don’t care at all,” said Dr. Joe Gerald, Medical Director at the University of Arizona. “And those groups are foregoing testing.”

Because so many people with COVID are home testing or not testing at all, there’s no accurate way to predict how many cases there are.

Except by testing wastewater.

“We communicate the data to the Pima County health department, make them aware of what’s going on,” Pepper said. “And helps them measure the efficiency and use of resources.”

Because of the complexity of the work, Pepper says it will be another two weeks before he can say for sure just what the numbers are.

“It’s still pretty high and there’s been an uptick recently,” he said. “And that’s really caused by BA-5.”

Right now, Pepper is testing two dormitories which are housing students for the summer and has seen a recent spike in cases in the past two weeks.

The results will be used to guide university policy when the students come back next month.

“In 2021 we managed to keep the university open in large part because of wastewater epidemiology,” Pepper said. “Whereas many universities across the country had to shut down.”

Saving the UofA an estimated $100 million he said.