The first Covid-19-related death on US soil came weeks earlier than previously thought, it has been confirmed. 

Autopsies on two people who died in California’s Santa Clara County on February 6 and February 17 have revealed they died from Covid-19, according to a newly released statement by Santa Clara County coroner's office. 

The Medical Examiner-Coroner says they sent samples from the two individuals to the Centers for Disease Control and Prevention (CDC) and received confirmation on Tuesday that the tissue samples from both cases tested positive for SARS-CoV-2, the coronavirus that causes Covid-19. 

The coroner statement has also confirmed that an individual who died in Santa Clara County on March 6 died of Covid-19.

"These three individuals died at home during a time when very limited testing was available only through the CDC," the coroner statement said, adding that testing at the time was restricted to people with a known travel history and who were showing specific symptoms.

Prior to these three cases, the first confirmed Covid-19 death in the US was in Seattle on February 26 and the first in the County of Santa Clara was on March 9.

While the first confirmed case of a Covid-19 infection (non-fatal) in the US was on January 20, this new information hints there might be more early unidentified cases of Covid-19, and the outbreak may have been circulating in parts of the US earlier than previously assumed.

“What these deaths tell us is that we had community transmission far earlier than our systems allowed us to detect. The virus was likely introduced and circulating in our community earlier than we had known,” Dr Sara Cody, health director in Santa Clara county, said in a statement to the media on Tuesday. 

When and where these undetected cases may emerge, however, remains unclear for now. Researchers are happy to admit the early timeline of Covid-19 is likely to change as more information comes to light, although they are fairly skeptical about anecdotal claims of many people saying they had the infection in November and December 2019. 

"I believe at the end of this, when we do look back – and we will – we will probably find that this disease was here earlier than we thought," Dr Georges Benjamin, executive director of the American Public Health Association, told USA Today in early April. However, Dr Benjamin added it's "plausible but not likely" that Covid-19 was in the US in November and December. 

At time of writing (April 23), the number of confirmed Covid-19 cases in the US has reached more than 842,000, and over 46,700 people have died, according to data collected by Johns Hopkins University. Worldwide, there have been 2,649,680 confirmed cases and 184,543 deaths, although the real figure is believed to be much higher.