By RACHEL LA CORTE and MARTHA BELLISLE, Associated Press

OLYMPIA, Wash. (AP) — Washington Gov. Jay Inslee is going to announce a ban on gatherings and events of more than 250 people in virtually the entire Seattle metro area, according to an Associated Press source, in an attempt to stop the spread of the new coronavirus.

The state has at least 24 COVID-19 deaths, the most in the U.S. The person who spoke about the decision late Tuesday was involved in the planning of the decision but spoke to the AP on condition of anonymity because they weren’t authorized to discuss the matter publicly. Inslee has scheduled a news conference in Seattle for late Wednesday morning.

The source said the ban would apply to King, Pierce and Snohomish counties, home to almost four million people. The order would not prohibit the operation of workplaces and is not expected to include school closures, the source said. It would apply to sporting events like Seattle Mariners baseball and Seattle Sounders soccer games.

Santa Clara County in California, home to San Jose and Silicon Valley, on Monday announced a ban on all gatherings of 1,000 people or more.

At least 24 people have died in Washington from COVID-19, most in the Seattle metro area. Nineteen of the deaths are linked to one suburban Seattle nursing home and authorities in King County said the virus has spread to at least 10 long-term care facilities

Late last month Inslee declared a state of emergency over the virus outbreak. There are more than 260 confirmed cases in the state, most in the three counties that would be affected by Inslee’s new order.

At least 10 long-term care facilities in the Seattle area have reported COVID-19 cases, with deaths at three of them — a worrying development as health officials have cautioned that the elderly and those with underlying conditions are especially at risk.

Inslee on Tuesday outlined a list of requirements for such centers aimed at stopping the worst coronavirus outbreak in the nation. A nursing home in Issaquah and another in Seattle each reported the death of a resident, bringing the total COVID-19 deaths in the state to at least 24. Nineteen of those deaths are tied to a Kirkland nursing home.

King County reported new cases were found in 10 long-term facilities where residents or staff or both have tested positive. The county reported an increase of 74 positive cases since Monday bringing the total to 190. Snohomish County said it had 54 confirmed cases. That brought the statewide total to more than 250, and Inslee said that number is likely much higher.

At a news conference Inslee also said the state is preparing for many more cases than have been reported, potentially tens of thousands, based on estimates of the spread of the disease.

“If we assume there are 1,000 or more people who have the virus today....the number of people who are infected will double in five to eight days,” Inslee said. “If you do the math, it gets very disturbing.”

The state has experienced the worst outbreak of COVID-19 in the nation.

The governor’s case estimate comes from a group of scientists who are contributing data to the decision-making in Washington state, communicating with phone calls and white papers “every day in some fashion,” said Trevor Bedford, a computational biologist at Fred Hutchinson Cancer Research Center.

His lab and collaborators at University of Washington and the Institute for Disease Modeling are sharing their analysis of infection rates and genetic clues linking the cases. Based on genome sequencing of 18 cases and the infection rate in the Seattle Flu Study, they believe there could be 1,100 active infections, Bedford said Tuesday.

For most people, the new coronavirus causes only mild or moderate symptoms, such as fever and cough. For some, especially older adults and people with existing health problems, it can cause more severe illness, including pneumonia.

The vast majority of people recover from the new virus. According to the World Health Organization, people with mild illness recover in about two weeks, while those with more severe illness may take three to six weeks to recover. In China, more than 80,000 people have been diagnosed and more than 58,000 have so far recovered.

Inslee said the state is implementing a list of new rules for these long-term care centers. Residents at these facilities will be limited to one visitor a day and they must host them in their rooms. All visitors must sign in and follow precautionary measures like social distancing, he said.

Employees must be screened for symptoms at the start of each shift and the facilities are not allowed to disclose confidential health information, he said.

The resident of the Issaquah Nursing and Rehabilitation Center died over the weekend and five other residents are in quarantine — two onsite and three offsite, the nursing home said. Two staff members also tested positive and are in an offsite quarantine. The center is awaiting results for tests on two other workers.

A man in his 80s who was a resident of Ida Culver House in Seattle was hospitalized at University of Washington Medical Center, and died Monday, King County health officials said.

Employees at the Life Care Center in Kirkland, linked to 19 virus deaths, have finally started getting tested for COVID-19, said Tim Killian, a spokesman for the nursing home. He said that about 30 had been tested by Tuesday, and that he believed arrangements were being made to test all 180 workers. Some 64 of the facility’s employees are showing symptoms and not working, he said, and two have returned to work after receiving medical clearance.

Forty-nine residents remain at the Life Care Center — 21 of them with positive coronavirus tests, and 16 with pending or inconclusive tests, Killian said Tuesday. Nearly three dozen others are in hospitals, including four who were transferred since Monday. Including all residents, those who are hospitalized and those who remain at Life Care, there are 55 positive -- 34 in hospitals, 21 at the nursing home.