NASHVILLE (AP) — A laboratory processing Nashville coronavirus tests did not report 312 positive results to the city for weeks, the Tennessean reported.

The delay hampered the city's contact tracing efforts and led to an artificial case spike in confirmed coronavirus cases as the results were added to Wednesday's and Thursday's totals.

Dr. Alex Jahangir, the leader of Nashville's coronavirus task force, said the city doesn't know if the test results were reported more quickly to the infected individuals.

The city sends test samples to labs, then the lab sends results to the Tennessee Department of Health, which relays them to the Nashville Metro Public Health Department. People who are tested get their results directly through a web portal updated by the lab.

"It could be that part of those people got delayed results and they weren't aware they were positive," he said. "Our hope is, if somebody was getting a test … they would self-isolate until they get results."

It was the third time Nashville test results were delayed by American Esoteric Laboratories, a company that until recently processed samples from test sites run by the city. Jahangir said the delay was one of the reasons the city recently replaced AEL with a new company, Pathgroup, which had "tremendously" reduced the wait times.

The delay reporting tests dating as far back as mid-June may have set back the city's efforts to slow an escalating outbreak. Nashville employs contact tracers to investigate the source of infections and identify clusters, but they can't trace infections if they don't know they exist. And those infected individuals may have been spreading the virus unknowingly for weeks.

The error also represents the larger challenge of the outbreak that has strained testing and tracing efforts across the U.S. The coronavirus is surging in many states, and most of them depend on a small group of laboratories to process millions of tests.

"We have heard of delays of seven, 10 and sometimes even 12 days to get results back from a test. That's unacceptable," Tennessee Health Commissioner Dr. Lisa Piercey said Wednesday. "We can't get patients back to work and we can't get contact tracing started until we get that result back in."

The delayed cases Thursday contributed to a single-day total of 688 new infections, the highest ever reported in Nashville.

During a call with Metro Council members, Nashville Health Director Michael Caldwell said the escalating infections have challenged the city's team of 125 contact tracers. The team will respond to the recent surge with a "blitz" of emergency tracing, he said.

Additionally, the state Supreme Court issued an order Thursday requiring anyone who enters a courthouse for court-related business to wear a facial covering while inside. The requirement kicks in Monday. Exemptions include those under age 12 and people with a medical reason for not wearing a mask.

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Follow AP coverage of the pandemic at https://apnews.com/VirusOutbreak and https://apnews.com/UnderstandingtheOutbreak.