The Santa Clara country medical examiner received confirmation from the Centers for Disease Control and Prevention on April 21 that tissue samples from two individuals who died at home on Feb. 6 and Feb. 17 had tested positive for COVID-19.
A third individual who died on March 6 also tested positive for the disease.
Those deaths occurred before what was previously believe to be the first confirmed COVID-19 deaths in the United States, which occurred on Feb. 26 outside of Seattle.
While Santa Clara health officials knew that there was COVID-19 in the country in February, local transmission in the community wasn't identified until February 28.
The three new cases indicate that the virus was spreading in the community to a significant degree earlier than they had realized, Santa Clara County Health Officer Dr. Sara Cody said during a press conference on Wednesday.
At the time of the deaths, there was a very narrow case definition for COVID-19 testing and health officials were only considering people with relevant travel histories.
The Santa Clara deaths included a 57-year-old woman and two men; one 69, the other, 70, the health officials said.
ABC News' Lauren Botchan contributed to this report.
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