Washington’s coronavirus caseload could climb dramatically – from 64,000 to 250,000 people -- if the state doesn’t take immediate action, Gov. Jay Inslee said Tuesday, as he announced new measures to stem the outbreak.

“If we are going to stop this epidemic or seriously slow it down, we need to look at what’s coming in Washington state,” Inslee said. “Not just what is here today.”

Washington is the hardest-hit state in the country with COVID-19. There are now 267 coronavirus cases in the state and 24 people have died, most associated with one nursing home.

Inslee said the state of 7 million people has many more undiagnosed cases of the disease, perhaps at least 1,000 right now, and without concerted steps to prevent the spread, the cases could double within five to eight days.

“If you do the math, it gets very disturbing,” Inslee said.

The extrapolation means that within two months if the state doesn’t act, 64,000 people could be infected in Washington within two months, he said, and could go up to 250,000 within two weeks after that. The calculation is based on consultation with Dr. Anthony S. Fauci, the director of the National Institute of Allergy and Infections Diseases, doctors with the World Health Organization and local experts, Inslee said.

He called it “the best assessment we have from our epidemiologists and we have spent hours and hours looking at the science on this because we’re a science-based state.”

Washington has now enacted new regulations for nursing homes. Among those new requirements, residents can have only one visitor per day and that visitor must be an adult and can spend time only in the resident’s room. Employees must also now be checked for COVID-19 symptoms at the start of each shift.

Officials in Oregon, which with 15 patients has far fewer known coronavirus cases than Washington, have said in the past that there could be a few hundred cases in the state.

As of Tuesday, Oregon state and regional health officials said the state hasn’t estimated a worst-case scenario of how many people might need serious treatment and when they would institute more measures.

The Oregon Health Authority did not immediately respond to questions about case estimates.

For now, Oregon health leaders urge residents to follow guidelines from the Centers for Disease Control and Prevention: Older adults and those suffering from a chronic condition like diabetes or heart disease should take steps to prevent infection by not traveling and by avoiding crowds, and they should stock up on supplies, food and medicine.

Later Tuesday, the state issued new guidelines for nursing homes, assisted living and residential care facilities, calling on them to curb community outings and restrict visitors to essential people only. Health officials also said visits by essential people should be only two per resident at a time and the visitors must be screened for respiratory or other symptoms tied to COVID-19 and for recent travel to coronavirus hot spots.

-- Fedor Zarkhin fzarkhin@oregonian.com desk: 503-294-7674|cell: 971-373-2905|@fedorzarkhin Subscribe to Oregonian/OregonLive newsletters and podcasts for the latest news and top stories.