The first American to die of COVID-19, the disease caused by the novel coronavirus that has become a global pandemic, succumbed weeks earlier than initially believed, officials in California said late Tuesday.

The Santa Clara Medical Examiner-Coroner said autopsies on two people who died in early and mid-February showed they had been infected by the virus. Samples sent to the Centers for Disease Control and Prevention (CDC) tested positive on Tuesday.

Until the new revelations, the first COVID-19 death had been identified as a man in his 50s in Washington state who died Feb. 29.

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The two people died at home on Feb. 6 and Feb. 17, making them the earliest-known victims of the coronavirus in the United States, the Santa Clara County public health department confirmed in a statement on Tuesday

The county health department said both individuals “died at home during a time when very limited testing was available only through the CDC.”

“Testing criteria set by the CDC at the time restricted testing to only individuals with a known travel history and who sought medical care for specific symptoms,” it added. “As the Medical Examiner-Coroner continues to carefully investigate deaths throughout the county, we anticipate additional deaths from COVID-19 will be identified.”

The first coronavirus cases were identified in California in early February, but the first case of community spread to someone with no known links to either a previous COVID-19 case or travel to risky places like Wuhan, China, was not identified until Feb. 26, when a resident of Solano County being treated in the Sacramento area tested positive for the virus.

Santa Clara County officials did not identify either of the two individuals who died, whether they had traveled to Wuhan or elsewhere, or whether they had contact with the few people who had been diagnosed with the disease before they died.

But reclassifying their deaths as related to the coronavirus suggests the virus had been spreading through the United States for much longer than was initially thought — potentially for weeks or even months longer.

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The first person to test positive for the coronavirus in the U.S., a Washington man in his 30s who had traveled to Wuhan, tested positive on Jan. 22. That patient recovered, but he is thought to have spread the virus to several other people in the state, kicking off the first known outbreak inside the United States.

Investigators will determine whether either of the Santa Clara deaths were connected to the Washington cluster, but it is likely that the virus arrived in different parts of the United States at different times, and from different places.

Genetic data from patients in New York show the virus they contracted likely came from contacts in Italy or other parts of Europe, while the Washington outbreak came from the American who traveled to Wuhan.

Santa Clara, home of Silicon Valley, has extensive air ties to both Asia and Europe, making the spread of the virus all but inevitable.

The new cases also underscore just how far behind American preparations for the coronavirus had fallen by early February. As countries like South Korea, Taiwan and China were ramping up testing operations that would eventually cover a sufficient portion of their population to control the virus, the United States response was hampered by a CDC-created test that did not work and a private sector that did not create its own tests that could operate at scale.

The first person in the United States to die of COVID-19, on Feb. 6, succumbed six days before California public health labs began testing for the coronavirus. At the time, California was sending all its samples to the CDC in Atlanta. The day the first person died, California had identified six cases, including two in Santa Clara County.

Jeffrey Smith, a doctor who serves as county executive for Santa Clara County, said at a briefing earlier this month that the virus could have been “freewheeling” in California for longer “a lot longer than we first believed,” the Los Angeles Times reported at the time.

“This wasn’t recognized because we were having a severe flu season,” Smith continued. “Symptoms are very much like the flu. If you got a mild case of COVID, you didn’t really notice.”

“You didn’t even go to the doctor. The doctor maybe didn’t even do it, because they presumed it was the flu,” he said.

Updated at 8:27 a.m.