The first recorded victim of the coronavirus in the United States was a 57-year-old woman in Santa Clara County who died at home on Feb. 6, and though her death was considered suspicious at the time, severe testing shortages across the country delayed her diagnosis more than two months, public health officials said Wednesday.

The stunning discovery, announced Tuesday night, has upended earlier accounts of when the virus was believed to have arrived in the United States. Previously, the first recorded coronavirus deaths were Feb. 26 in Washington state. The new fatality was three weeks earlier. And given what’s known about how much time passes between the initial infection and death, the woman was probably infected in early January.

Her death became linked to the pandemic because the medical examiner had questions about unidentified viral infections that killed the woman and two men, and thought to save their tissue, said Dr. Sara Cody, the Santa Clara County health officer. The men also tested positive for the coronavirus posthumously.

Though all three Santa Clara County cases remain under investigation, so far it appears they were infected by community transmission — meaning the specific source of exposure cannot be identified, Cody said. None of the three had traveled outside the country shortly before they died or were known to have had contact with someone diagnosed with the coronavirus.

“These three individuals died at home during a time when we had very limited testing,” Cody said. “Now, in retrospect, we can look at these deaths, and these deaths let us know that we had more widespread transmission than we had previously understood or documented.

“Cases like these deaths likely represent the tips of icebergs of unknown size, and represent an unknown number of cases that have gone undetected in our community,” she said.

Public health and infectious disease experts said that although the newly identified cases demonstrate that the coronavirus came into the United States far earlier than previously understood — the first reported case was Jan. 21, in Washington — it’s still difficult to say how widespread the virus was in the early days of the pandemic.

The first cases were reported in China at the end of December. But some infectious disease experts have suggested that the virus may have started to spread in November, or even earlier. Given how much travel there is between China and the United States — and in particular Silicon Valley — it would not be surprising if the virus arrived in Santa Clara County not long after it emerged in China, said George Rutherford, an infectious disease expert at UCSF.

He added that these earlier deaths may explain why Santa Clara County was harder hit by the virus than anywhere else in the Bay Area. If it arrived there first, it makes sense that the county would have more cases and more deaths. As of Wednesday, Santa Clara County had nearly 2,000 cases, or more than a quarter of the Bay Area total.

“You can only imagine the back and forth that was happening between Silicon Valley and China,” Rutherford said. “This starts to explain the dynamics of why Santa Clara County is worse than the rest of the Bay Area.”

But Rutherford and other infectious disease experts said they doubted that there was rampant transmission of the coronavirus in January and February. There were certainly more cases than have previously been reported — and Cody too said she expected to identify more deaths from earlier in the year — but they likely were isolated events.

The woman who died Feb. 6 was Patricia Dowd, a seemingly healthy 57-year-old San Jose woman who was recovering from flu-like symptoms, her family told the Los Angeles Times. Two hours before she was found dead, Dowd, a manager for a semiconductor firm, had been working from home, communicating with a colleague. Her death was believed to have been caused by a heart attack, the Times reported.

The two other victims were a 69-year-old man who died Feb. 17 and a 70-year-old man who died March 6. Officials did not name any of the victims. Previously, the first reported death from COVID-19 in Santa Clara County was March 9.

All three people died in the thick of the flu season, and it’s possible that many other early COVID-19 cases were mistaken for influenza, infectious disease experts said. The illnesses have similar symptoms, and in January and even February, many doctors wouldn’t have thought to look for the coronavirus in patients who appeared to have the flu.

And back then, it was impossible to test the vast majority of people with COVID-19 symptoms for the virus because there weren’t enough tests available, and the Centers for Disease Control and Prevention severely restricted who was allowed to be tested.

Dr. Michelle Jorden, the chief medical examiner-coroner who preserved tissue from the victims, said that collecting such samples at the time of death is standard protocol when a person dies from an unidentified viral infection. But she noted that those cases were especially concerning: They were all people who had specific coronavirus symptoms and who had died with viral pneumonia.

“We really had suspicion that these could potentially be COVID-19,” Jorden said. “And that’s why we pursued these additional tests through the CDC.”

Jorden said the samples were sent to the CDC for testing in mid-March, and the results were returned Tuesday. Though tests involving posthumous tissue samples are similar to those used to diagnose living cases, the county public health laboratory did not have the necessary equipment to test the samples locally, she said.

At his daily briefing Wednesday, Gov. Gavin Newsom said the state has “directed (counties) beyond just Santa Clara to go back as far as December to request the coroners’ autopsy to dig even deeper.”

“We are very pleased with the work that was done in Santa Clara County to make public that information, and know that we are doing the same across the state, in other counties as well, to ultimately help guide a deeper understanding of when this pandemic really started to impact Californians directly,” he said. “When this occurred is important forensic information, profoundly significant in terms of understanding the epidemiology of this disease.”

San Mateo County officials said their coroner’s office has tested every body for the coronavirus since mid-March. The office is considering revisiting earlier deaths too, said Coroner Robert Foucrault. But it won’t be an easy task.

“We don’t have a mechanism to look at just respiratory deaths, we’d have to review every file,” Foucrault said. “It’s involved. There are a lot of things we have to go back and take a look at: the cause of death, see if there are signs and symptoms of COVID-19 from medical records.”

Cody said she “applauded” the Santa Clara County medical examiner for following up on the early cases. She said the discovery of these earlier deaths is further proof that the county and the rest of the country would have benefited from more widespread testing earlier in the pandemic.

“I know that in late January and through the month of February, we were very anxious at our inability to test people who we thought might have had COVID-19,” Cody said. “There just wasn’t the capacity there. We were anxious that there was a lot of transmission that was going undetected. What these cases tell us is that we were right to be anxious.”

Cody said it is now clear that there was more transmission of COVID-19 than previously believed when the county pushed for shelter-in-place restrictions in March, and with five other Bay Area counties became the first in the nation to impose them.

“If we had had widespread testing earlier and been able to document the level of transmission in the county, if we had understood then that people were dying — yes, we probably would have acted earlier than we did,” she said.

UCSF’s Rutherford said it will be important now to determine how all three newly identified victims might have been infected — whether it was from community spread in early January, or from contact with an individual who was known to have recently traveled to China.

But perhaps just as important will be determining whether they transmitted the virus to anyone else, he said. It’s important to note that these early cases do not appear to have sparked a large outbreak — and understanding why not could offer clues to controlling the virus over the coming months.

“What’s going to happen this summer is we’ll have small outbreaks all over the place,” Rutherford said. “These cases could be informative. These tell stories about how this virus extinguishes in the wild, before you start imposing quarantine and isolation. That’s an important question to understand.”

San Francisco Chronicle staff writers Joaquin Palomino and Alexei Koseff contributed to this report.

Erin Allday and Matthias Gafni are San Francisco Chronicle staff writers. Email: eallday@sfchronicle.com, matthias.gafni@sfchronicle.com Twitter: @ErinAllday, @mgafni