California Gov. Gavin Newsom asked coroners to review deaths dating back to December to "guide a deeper understanding of when this pandemic really started to impact" the state.

"When this occurred is important forensic information, profoundly significant in understanding the epidemiology of this disease," Newsom said.

This decision came after new autopsy results showed that COVID-19 killed two people in Santa Clara County on February 6 and 17, weeks earlier than the deaths previously considered the state's earliest.

The US had 23 confirmed coronavirus cases on March 1, but a new model estimates that 28,000 people had already been infected.

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California Gov. Gavin Newsom has tasked coroners and medical examiners with reviewing the state's deaths as far back as December to see when people really started dying of COVID-19.

At a press briefing on Wednesday, Newsom asked them to "dig even deeper" and conduct autopsies on people who may have died of coronavirus long before it was known that the illness had spread to California, according to the Mercury News.

The goal, Newsom said, is to "guide a deeper understanding of when this pandemic really started to impact Californians directly," the Hill reported.

"When this occurred is important forensic information, profoundly significant in understanding the epidemiology of this disease, all of those things are brought to bear with more clarity and light," the governor told reporters. "Not only because of this specific announcement, but I imagine subsequent announcements that may be made by similar efforts all across the state of California."

The announcement Newsom was referring to was that autopsy results this week revealed that COVID-19 killed two people in Santa Clara County on February 6 and 17. That's at least three weeks earlier than the coronavirus death California officials previously considered the state's first. The US's recorded its first coronavirus death on February 28 in Washington state.

A medical professional administers a coronavirus test at a drive-thru testing location conducted by staffers from University of California, San Francisco Medical Center (UCSF) in the parking lot of the Bolinas Fire Department, April 20, 2020 in Bolinas, California. Ezra Shaw/Getty Images

Dr. Sara Cody, Santa Clara County's Health Officer, said on Wednesday that the newly confirmed coronavirus deaths were a 57-year-old woman and a 69-year-old man, according to the Mercury News. Both cases seem to have been acquired via community spread.

"If we had understood then that people were already dying, then yes, we probably would have acted earlier than we did," Cody said.

The US has reported more than 873,200 coronavirus cases and at least 49,700 deaths. Of those, 39,00 cases and 1,500 deaths have occurred in California, according to data compiled by Johns Hopkins University.

Indiana is also attempting to trace cases back to mid-February. The state reported its first death on March 16, but officials revised that date to March 10 earlier this month, according to the Indianapolis Star.

The coronavirus was first reported in Wuhan, China, in late December, though some evidence suggests it was circulating there as early as mid-November.

A model from researchers at Northeastern University suggests that the coronavirus had started spreading in New York, San Francisco, Chicago, Boston, and Seattle by early February. Thousands of people were probably unknowingly contracting the disease, The New York Times reported.

On March 1, 23 coronavirus cases had been reported in those five major cities, but the Northeastern researchers calculated that the real tally was closer to 28,000. By the end of February, the virus had likely already been transported across the nation, the Times reported.