As of early March, people have tested positive for the coronavirus in about 70 countries. Officials are taking "unprecedented" actions. (Video: The Washington Post)

California reported its second case of community transmission of the coronavirus Friday, and Oregon and Washington announced others just hours later, providing fresh evidence that the deadly virus is circulating in the United States.

Authorities in Santa Clara County, Calif., said a 65-year-old woman had come down with the covid-19 disease without traveling to any countries hit hard by the outbreak or coming in contact with anyone known to have the infection.

In Oregon, officials said a person from Washington County, in the northwest part of the state, had tested positive under similar circumstances. The positive test was conducted by the state’s laboratory and is considered “presumptive” until it is confirmed by the federal Centers for Disease Control and Prevention.

The unnamed Oregon individual was an employee of Forest Hills Elementary School outside Portland but has a job that “does not typically come into contact with students,” the Lake Oswego School District wrote to parents in an email obtained by local news. The “few individuals” who did have close contact with the infected person were asked to stay home from work or school for two weeks.

The school will remain close through Wednesday as it is cleaned, the district told parents.

In Washington, state health officials said a high school student in Snohomish County, just north of Seattle, received a “presumptive” positive test in another case of unknown origin.

The Jackson High School student was not in school most of this week, but was on campus briefly Friday morning, according to a statement from Everett Public Schools. Students who were in contact with the patient will remain home for 14 days while health authorities monitor their symptoms, and the school will close for three days, the school district said.

The developments mean the virus is spreading in at least four separate communities — two of them about 90 miles apart in California, and two others farther up the West Coast. On Wednesday, authorities revealed the nation’s first case of community transmission, a woman in Solano County, Calif.

There is no apparent connection between the new California patient and anyone else with the disease, including the Solano County case and two previous cases in Santa Clara County, said Sara Cody, the Santa Clara County health officer.

“I think there’s a strong possibility that there’s local transmission going in California,” said Jennifer Nuzzo, senior scholar at the Johns Hopkins Center for Health Security. “In other words, the virus is spreading within California, and I think there’s a possibility other states are in the same boat — they just haven’t recognized that yet.”

Two students in Palo Alto, a city of 67,000 in the northwestern corner of Santa Clara County, also may have been exposed to the virus, according to a letter to parents from the schools superintendent Friday.

The children are from the same family. One is in high school and the other is in middle school.

The school system said that “as a precautionary measure, the district immediately took action and the two students were sent home and will be excluded from attending school until we receive more information.”

The virus that has been reported in 56 countries is now reaching into the heart of Silicon Valley, home to some of the world’s largest technology companies — including Google, Apple and Tesla — and San Jose, a city of 1 million people. Santa Clara County is home to 2 million residents.

The three tech giants and other companies based in Santa Clara County did not respond to requests for comment on whether they are taking new precautions in response to the local case.

In a news release, Cody described the newly diagnosed Santa Clara County patient as “an older adult woman with chronic health conditions who was hospitalized for a respiratory illness.”

The virus is known to cause more severe illness in older people and those with underlying illnesses such as cardiovascular disease and diabetes. But the symptoms are milder in more than 80 percent of current patients.

Cody said at a news conference that the woman came to a hospital complaining of difficulty breathing. A physician treating her notified the county health department Wednesday evening because the patient’s symptoms seemed compatible with covid-19. The doctor asked for a coronavirus test, which came back from the county’s lab Thursday evening, Cody said.

Little else is known about the woman’s case, including her condition or how long she was in the community while infectious.

In Oregon, officials were trying to determine the number of close contacts the patient had, to help determine the potential spread of the disease.

“Contact tracing is our top priority right now,” said Oregon Health Authority Director Patrick Allen.

The Oregon patient, whose age and gender were not disclosed, is at Kaiser Permanente Westside Medical Center in Hillsboro, health officials said.

In Washington, health officials said the student who tested positive was a minor and had visited Seattle Children’s North Clinic on Feb. 24. Officials said they were tracing people who may have been exposed to the patient.

“Given the extent of global spread, we expect to identify more individuals with covid-19 in Washington,” State Health Officer Dr. Kathy Lofy said in a statement.

To date, the virus — which originated in Wuhan, China — has sickened more than 84,000 people and has killed more than 2,800, mostly in China. Outbreaks in some places, such as South Korea, Iran and Italy, have been particularly severe.

Santa Clara health officials warned residents in a news release that “now is the time to prepare for the possibility of widespread community transmission.” The county will be conducting surveillance to determine how widely the disease has spread, she said.

“I understand this may be concerning to hear, but this is what we have been preparing for,” Cody said. “Now we need to start taking additional actions to slow down the spread of the disease.”

Public health measures, such as contact tracing, isolation and quarantine, have helped slow the spread, she said, but other public health measures are now needed.

“What we know now is the virus is here and present in some level,” she said. “But we still don’t know to what degree.”

On Tuesday, the CDC warned Americans to prepare for the inevitable spread of the virus in their communities. If transmission becomes more widespread, that could mean school closings, companies mandating telework and limits on or postponements of mass gatherings, said Nancy Messonnier, a top CDC official.

The CDC has also been under intense pressure to step up testing for the virus to determine how far the disease has spread. The agency promised Friday that it would be providing more test kits to states in coming days to allow for more rapid identification of infected people.

The discovery of two more cases “supports what we are trying to do with basic infection control and case identification,” said Saskia Popescu, senior infection prevention epidemiologist for Honor Health, a hospital system in Phoenix. “We need to focus on pragmatic and scientifically based measures and not hit the panic button. We know how to protect ourselves.”

Cody advised people to wash their hands and try not to touch their faces. Families should discuss supplies that might be needed if someone needs to stay home for a week or two. Schools should explore online learning, she said.

“I do understand the whole situation may feel overwhelming, and it’s difficult to think about the possible disruption in our everyday lives, especially when we are still uncertain about what this may look like,” she said. “But we do need everyone to start thinking about what actions they can take now so we can be prepared for the possibility of further spread of the virus in our community.”

Greene reported from Seattle. Christina Passariello and Heather Kelly in San Francisco and Derek Hawkins, Amy Goldstein and Ashley Parker in Washington contributed to this report.

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