Health officials in California's Santa Clara County have identified two people who died from the new coronavirus in early and mid-February, making them the earliest known victims of the outbreak in the United States.
It was previously thought that the first US death from COVID-19, the respiratory disease caused by the virus, was a man in his 50s who died in Washington state on February 29.
The testing parameters set at the time by the CDC restricted testing to individuals with a known travel history and who sought medical care for specific symptoms.
News of the deaths in California could improve public health officials' understanding of how the outbreak took hold in the United States.
US coronavirus deaths topped 45,000 on Tuesday, doubling in a little over a week and rising by a near-record amount in a single day, according to a Reuters tally.
The United States has by far the world's largest number of confirmed coronavirus cases at more than 810,000, almost four times as many as Spain, the country with the second-highest number.