Santa Clara health officials confirmed the test results Tuesday. One of the victims died on February 6, and the other died on February 17.
The first official recorded death in the nation from the virus was reported on 29 February in Kirkland, in the state of Washington.
"Models of epidemic spread in the USA will have to be adjusted to account for an earlier start date", Jay Bhattacharya, a professor of medicine at Stanford University told AFP.
"What these deaths tell us is that we had community transmission far earlier than our systems allowed us to detect".
Dr. Cody's opinion was echoed by Dr. Ashish K. Jha, director of the Harvard Global Health Institute.
Eighty-eight of them died and 175 are hospitalized.
"These three individuals died at home during a time when very limited testing was available only through the CDC", the county said in a statement. "As the Medical Examiner-Coroner continues to carefully investigate deaths throughout the county, we anticipate additional deaths from Covid-19 will be identified".
Another person who died in Santa Clara County on March 6 also had the disease caused by the coronavirus, the medical examiner-coroner said in a statement. A third autopsy found another patient died from coronavirus on March 6. "More investigation will be done to try and confirm that that's the case".
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As Cody explains it, each severe covid-19 case or death "represent tips of icebergs of unknown size".
"When you start seeing the first death, actually, the number of cases in the population is probably pretty high already".
"(It) shakes me up a little bit", Sepkowitz, an infectious disease specialist, told CNN Wednesday.
"In other words, all of the country monitors flu-like illness generically, over time". "This tells us that yes, we were definitely missing cases".
Previously, the first known possible instance of community spread of novel coronavirus in the U.S. - in which a patient didn't have relevant travel history or exposure to another known patient - was announced by the CDC on February 26.
Coronavirus deaths in the U.S. topped 46,000 on Thursday, doubling in a little over a week. Preliminary results were announced in the last few days. And in Los Angeles County, scientists put the true number of infections at around 40 times the actual case count.
There are 2,018 confirmed COVID-19 cases and 98 deaths in Santa Clara County so far, according to data released by the county's Public Health Department on Friday morning. That represents between 48,000 and 81,000 people - and 50 to 85 times the cases that county officials recorded by that date.