SAN FRANCISCO — Officials in Santa Clara County, Calif., announced late Tuesday that two residents there died of the coronavirus in early and mid-February, making them the earliest known victims of the pandemic in the United States.
The new information may shift the timeline of the virus’s spread through the country weeks earlier than previously believed.
The first report of a coronavirus-related death in the United States came on Feb. 29 in the Seattle area, although officials there later discovered that two people who had died Feb. 26 also had the virus.
But Santa Clara County officials said that autopsies of two people who died at their homes on Feb. 6 and Feb. 17 showed that the individuals were infected with the virus. The presence of the disease Covid-19 was determined by tissue samples and was confirmed by the Centers for Disease Control and Prevention, county health officials said in a statement.
“Each one of those deaths is probably the tip of an iceberg of unknown size,” Dr. Sara Cody, the county’s chief medical officer, said in an interview. “It feels quite significant.”
Dr. Cody said the individuals who died in February did not have any known travel histories that would have exposed them to the virus, which first appeared in China. They are presumed to have contracted the virus in the community, she said.
The newly reported deaths suggest that the coronavirus may have been spreading in California much earlier than was previously known, said Dr. Jeffrey V. Smith, the Santa Clara county executive and a medical doctor.
“It was probably around unrecognized for quite some time,” Dr. Smith said.
It was unclear early Wednesday why it had taken so long to identify the February deaths as caused by the coronavirus.
Much debate has centered on the question of when the virus arrived in the United States and how early it began to spread among people. Problems and delays slowed the availability of widespread testing for the virus, which has killed more than 40,000 people nationwide.
In January, the authorities identified a series of coronavirus cases from travelers abroad, but they did not identify any community spread of the virus for several weeks.
The federal government had strict rules on who qualified for coronavirus testing, and test kits developed by the C.D.C. — that public health labs began receiving on Feb. 7 — turned out to be faulty. Strict definitions of who could be tested limited what local health officials could do to find out how widespread the virus might be.
“We had to ask the C.D.C. every single time: Does this person meet the case definition? May we send a sample?” Dr. Cody said.
“We had this very, very uncomfortable feeling that we were hearing about a lot of patients who really felt that they were cases but we couldn’t test,” she said.
Other indications have emerged that the virus may have been spreading earlier than previously known. The Grand Princess cruise ship that departed San Francisco on Feb. 11 had passengers who developed the coronavirus on board. Researchers believe that the virus also began to circulate in the New York area by mid-February. And in early March, researchers found a range of cases with genetic similarities to each other in the Seattle area, suggesting that it had been spreading undetected for weeks.
In Santa Clara County, Dr. Cody said that the picture of the spread was becoming clearer but that there were still gaps.
“We had so few pixels you could hardly pick out the image,” she said. “Suddenly we have many pixels that all of sudden that we didn’t even realize that we were looking for.”
But, she added, “I can’t put the story together yet.”
On March 16, Santa Clara County was among the first counties in the nation to announce stay-at-home orders. “Clearly in retrospect that was a good decision,” Dr. Cody said. “Now we see there was even more transmission than we recognized.”
Although California was an early state to report that individuals were carrying the virus, it has had one-tenth the number of deaths as New York State, the hardest-hit place in America. Officials believe that the early imposition of stay-at-home orders and the state’s lower population density are among factors that have helped California avoid the worst so far.
Thomas Fuller reported from San Francisco and Mike Baker from Seattle.
