WASHINGTON — The coronavirus has been circulating undetected and has possibly infected scores of people over the past six weeks in Washington state, according to a genetic analysis of virus samples that has sobering implications for the entire country amid heightening anxiety about the likely spread of the disease.

The researchers conducted genetic sequencing of two virus samples. One is from a patient who traveled from China to Snohomish County in mid-January and was the first person diagnosed with the disease in the United States. The other came from a recently diagnosed patient in the same county, a high school student with no travel-related or other known exposure to the coronavirus. The two samples look almost identical genetically, said Trevor Bedford, a computational biologist at Fred Hutchinson Cancer Research Center in Seattle who announced the results of the research on Twitter late Saturday night.


“This strongly suggests that there has been cryptic transmission in Washington State for the past 6 weeks,” Bedford wrote. “I believe we’re facing an already substantial outbreak in Washington State that was not detected until now due to narrow case definition requiring direct travel to China.”

Officials in Seattle and King County on Sunday announced that four more people have tested positive for the coronavirus, including the second person in the state to die of the virus. That brings the outbreak in Washington state to 13 cases. Of the four new cases, the three surviving patients range in age from their 70s to 90s, have underlying health conditions and are in critical condition, health officials said. The first coronavirus death in the United States, which was announced Saturday.

Health officials in Washington state and across the nation said they expect numbers will continue to rise in the wake of the decision by the U.S. Centers for Disease Control and Prevention last week to widen testing guidelines. Over the weekend, new cases were reported in Americans who had recently traveled to South Korea and Italy, including one person in Rhode Island, the state’s first case.

The health department in Santa Clara County, California, in the heart of Silicon Valley, announced three new coronavirus cases Sunday evening, bringing to seven the total number of cases there. The announcement gave few details about the cases.


Late Sunday, the office of Florida Gov. Ron DeSantis, a Republican, announced two “presumptively positive” cases of the coronavirus, in Manatee and Hillsborough counties, and declared a public health emergency.

California and Oregon, like Washington, have reported coronavirus infections in people who did not travel to regions hit hard by the outbreak or have contact with people known to be infected. The United States has dozens of other confirmed infections, the majority of them people who were among the passengers on the cruise ship Diamond Princess.

The international picture has continued to worsen, with spikes in cases in South Korea, Iran and Italy in recent days. Worldwide, almost 90,000 people have been infected with the coronavirus, and 3,000 have died.

The research reported by Bedford is preliminary, and further analysis could alter the conclusion. Bedford said it is possible but very unlikely that the genetic similarity of the two virus samples could be a coincidence and reflect two distinct introductions of the virus into Snohomish County by infected travelers, rather than sustained person-to-person spread within the community.

The CDC has been in touch with Bedford, and although agency experts note that his hypothesis has validity, scientists need more data, according to a Department of Health and Human Services official, who spoke on the condition of anonymity to talk candidly. “It is far from definitive,” the official said. The particular strain found in these two samples is widespread in China and elsewhere. It’s possible that someone else introduced the virus into the community “that we didn’t pick up,” the official said.


But this research could be evidence that the highly contagious virus has eluded efforts to contain it through travel bans, quarantines and other interventions. The virus may have been spreading in parts of Washington state among people who didn’t realize they were infected by it — they may have thought they had a cold or the flu.

On Saturday, state and King County health officials reported a possible coronavirus outbreak at the Life Care Center in Kirkland, Washington, a long-term residential facility where more than 50 residents and staff are reportedly ill with symptoms associated with the novel virus. At least two of King County’s six confirmed cases are connected to the Life Care facility: a health-care worker in her 40s and a resident in her 70s.

A statement released by the nursing home said that the residents typically exhibit cold and flulike symptoms at this time of year and that they may be sent to a hospital for covid-19 testing. “As precaution, all visits to the facility from families, volunteers or vendors are not allowed,” the statement said.

If the number of confirmed cases climbs dramatically in the next few days, it could reflect expanded detection efforts rather than a sudden increase in the rate at which the virus is spreading.

“Once we start testing more broadly this week, we are almost certain to learn that there has been community transmission for a while in many places,” said Andy Pavia, chief of the Division of Pediatric Infectious Diseases at the University of Utah health system. He called the Washington state research on the genetics of the virus “very important.”

Until a few days ago, the CDC had specific, narrow criteria for who should be tested for possible coronavirus infection — and most tests had to be sent to Atlanta due to faulty tests sent out to state labs. The focus was on people who had been to China or been in contact with someone who had traveled there. As a result, people with respiratory infections and fevers were not being widely tested for coronavirus. Last week, the CDC altered the criteria to expand testing.

Clinicians always have discretion to request testing, the CDC has said. A top CDC official said last week that no such requests for testing have been turned down.

Even so, a 56-year-old woman in Chevy Chase, Maryland, who recently returned from Northern Italy, where the virus has spread dramatically, and who has suffered from a cough and flulike symptoms for 10 days, told The Washington Post that she could not get a coronavirus test at a hospital because she was not hospitalized or severely ill.

“It’s almost impossible to get a damn test,” she said. The woman, a consultant who spoke on the condition of anonymity for fear of online harassment, said she normally commutes by train to downtown Washington to work but has self-quarantined since returning from Italy. Had she not chosen to do so, she said, “I could have been passing this all over D.C.”

A 30-year-old man who flew from virus-stricken Japan into Newark, New Jersey’s airport on Tuesday said he checked into NYU Langone’s emergency department in Cobble Hill, Brooklyn, with a 102-degree fever and cough. But because he did not meet the criteria as set at that time by the CDC — he lacked chest pains or shortness of breath — he was not tested for covid-19.

The man, who spoke on the condition of anonymity because he did not want to be associated with the outbreak, told The Washington Post he would be self-quarantined in his Brooklyn apartment for the next two weeks.

“My thought process was: Whatever I had, now it’s starting to get worse, so I better go to the hospital.” He wrote about his experience on the social media site Reddit.

After he arrived at the hospital, he was tested for flu strains and dozens of other microbes, all of which came back negative. A chest X-ray also returned negative. On Thursday he was informed that the CDC had not approved his case for testing because his symptoms were too mild.

He was sharing his story because he “wanted people to realize that there are probably more people like me.” His flight from Japan into Newark on Tuesday was full, he said.

“At no point am I saying ‘I have coronavirus.’ I’m just saying I have symptoms that are like it, and no one is testing me,” he said.

“All NYU Langone Health facilities follow the testing guidelines and infection prevention protocols issued by the CDC and state and city Departments of Health,” Lisa Greiner, a spokeswoman for NYU Langone, said in a statement. “As the situation concerning COVID-19 remains fluid, we are continually aligning our testing protocols to ensure the safety and welfare of our patients and staff.”

This weekend marked a clear turning point in the coronavirus crisis in the United States, with the first reported death and additional cases of community spread. As of Sunday afternoon, the CDC had listed nine cases in the United States of person-to-person spread.

Although the World Health Organization has declined to describe covid-19 as pandemic, the illness has spread to every continent but Antarctica, and there is widespread agreement among infectious disease experts that a significant fraction of the human population could become exposed to it in the coming year or two.

Vice President Mike Pence on Sunday offered assurances that the administration has a handle on the crisis and that the threat to most Americans is low. He said the Trump administration is leading an aggressive, whole-of-government response to the coronavirus and pointed to the president’s order to restrict travel from China as key to keeping Americans safe.

“I think it’s all a reflection of the fact that early on in this crisis, in January, the president took the unprecedented step of suspending all travel from China and establishing a quarantining effect,” Pence said on CNN’s “State of the Union.”

On the same show, former vice president Joe Biden criticized the administration’s response so far, saying there should have been more protective gear and test kits available sooner.

“We knew this was coming. Back as far as January. They didn’t even begin to prepare the testing kits. This is something that’s elementary,” Biden said.

Health and Human Services Secretary Alex Azar declined to comment on how many cases the United States may be facing. “We cannot make predictions as to how many cases we’ll have, but we will have more, and we will have more community cases,” he said on CBS’s “Face the Nation.” “It’s simply just a matter of math.”

___

The Washington Post’s Carolyn Y. Johnson, Alex Horton, Meryl Kornfield and Tory Newmyer contributed to this report.