The coronavirus may have spread undetected in the U.S. for weeks, a gene sequencing analysis found, according to The New York Times.

Researchers determined that the genomes of two coronavirus infections in Washington state show the virus could have spread in the state for almost six weeks. The two infections in Snohomish County shared a rare genetic variation, indicating they likely were related, the Times reported.

The infections concerned the first confirmed case in the U.S. on Jan. 20, which involved a man in his 30s, and another, involving a teenager, that was confirmed on Friday.

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This means the virus likely was spreading in between, Trevor Bedford, an associated professor at the Fred Hutchinson Cancer Research Center and the University of Washington, said, according to the Times.

Bedford said it's possible the two cases are unrelated but that it's unlikely, as only two out of 59 sample sequences from China had the genetic variation found in both cases. More than 125 genomes from samples around the world have been analyzed by the scientists.

According to this #SARSCoV2 genetic analysis the viral strain in Washington State traces to a Chinese strain from Fujian, likely arriving in Seattle area before January 15.

If this is true, #COVID19 has been in the area, undetected, for 6 weeks.https://t.co/tVuFN7EnQa pic.twitter.com/IuazcYLd8O — Laurie Garrett (@Laurie_Garrett) March 1, 2020

Mike Famulare, a principal research scientist at the Institute for Disease Modeling in Bellevue, Wa., conducted the analysis and said his “best guess, with broad uncertainty” is that between 150 and 1,500 people may have the virus, with the likely range being between 300 and 500 people, according to the Times. He said the patients have either been “infected and recovered” or are “infected now.”

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Washington Gov. Jay Inslee Jay Robert InsleeBarr asked prosecutors to explore charging Seattle mayor over protest zone: report Bottom line Oregon senator says Trump's blame on 'forest management' for wildfires is 'just a big and devastating lie' MORE (D) has declared a state of emergency amid at least eight confirmed cases in the state and one death confirmed Saturday. Two cases were confirmed in King County, Wa., Sunday, according to The Washington Post.

Rhode Island also confirmed its first case Sunday.

The U.S. is asking people to avoid traveling to mainland China, South Korea, Italy and Iran.