Six of the 18 Western Washington residents with the coronavirus have died as health officials rush to test more suspected cases and communities brace for spread of the disease. There were no confirmed cases of COVID-19 east of the Cascades, although three people are ill and await test results.

All confirmed cases of the virus in Washington are in Snohomish and King counties. The four most recent deaths occurred in a nursing home and most of the deceased had underlying health conditions.

Three counties in the Inland Northwest have sent samples to the Washington Department of Health’s lab in Shoreline for people they consider to be under investigation for the coronavirus..

There are more than 100 people diagnosed with COVID-19 in 11 states.

Some cases in Washington state include travelers returning from abroad. Others have no known connection to travel or contact with an infected person.

Health officials are preparing to see an increase of cases as testing capabilities expand.

“We expect the number of cases to increase in the next days and weeks, and we’re taking this situation very seriously,” King County health officer Dr. Jeff Duchin said Monday at a news conference. “The risk for all of us to become infected is increasing.”

The majority of people with COVID-19 will have mild symptoms, said Kathy Lofy, Washington’s health officer. Some will have severe illness and require hospitalization. State and King County health officials said on Monday COVID-19 is more dangerous for people with underlying health conditions and those over the age of 60.

“There are likely many mild cases in the community that we’re not aware of,” Duchin said. “The cases our health care colleagues are finding are the tip of the iceberg: patients that are hospitalized with severe illness.”

In future days and weeks, Duchin said the public health response will likely shift to not counting the number of positive COVID-19 cases but instead working on a community-based approach, like what is done with influenza.

“We are going to see a lot of sick people, and we will have a tremendous challenge on our health care system,” Duchin said.

Spokane County Regional Health District sent a sample for one person, affiliated with Gonzaga University, on Saturday for testing, but it was not delivered until Monday and results will likely be available in coming days.

To be tested for COVID-19, a person must display symptoms in addition to having traveled to China, Iran, Italy, Japan and South Korea recently or being in close contact with a person who has a confirmed case of COVID-19. Additionally, health care providers can test a person with severe respiratory illness who is hospitalized with no apparent cause for their illness. This measure is how doctors at EvergreenHealth Medical Center found COVID-19 among patients due to community spread, including at Life Care Center, an assisted living facility in Kirkland.

The person from Gonzaga is restricted from being in contact with others until their test results come back. University officials would not give further details about why they were tested beyond that they were following their medical provider’s advice.

Kelli Hawkins, spokeswoman for the SRHD, confirmed the Gonzaga-affiliated person is not one of the Gonzaga students who was studying abroad in Italy but then called home. Two patients with confirmed cases of COVID-19, who were passengers on the Diamond Princess cruise ship in Japan, remain in satisfactory condition at Providence Sacred Heart Medical Center, Hawkins said.

“In our community, at this time, we have no confirmed cases of COVID-19, so we are still at a low risk,” Hawkins said.

Health officials in Stevens County sent a COVID-19 test for a returning traveler who met testing requirements on Sunday. Concerns led the Northeast Tri County Health District to close Colville schools and activities on Monday until the test results are completed. The health district did not elaborate on the person’s role at Colville schools but did confirm the person is isolating themselves at home while awaiting test results.

One person from Grant County also has been tested for COVID-19, but county officials would not elaborate on the details of that case. Test results are expected within five days.

The state just started testing for COVID-19 late last week, due in part to delays at the Centers for Disease Control and Prevention to roll out statewide testing, as reported by ProPublica. As of Sunday night, Washington’s health department lab had tested 99 samples from 56 patients for COVID-19. Lofy expects that capacity to increase to up to 200 tests per day. The University of Washington will begin testing samples this week, she said at a news conference Monday.

“We have not detected cases outside of King and Snohomish counties,” Lofy said, “but given the movement, it is possible the virus is appearing in other counties, too.”

King County health officials aren’t recommending cancellation of large events or closing schools. However, they did caution people older than 60 or those with chronic health conditions to consider avoiding large group gatherings. Statewide, health officials encourage individuals to stay healthy by regularly washing hands with soap and water or alcohol-based hand sanitizer, covering coughs and sneezes, and staying home from work or school when sick.

Health officials asked the public to refrain from buying masks so health care workers can have access to the supplies. People experiencing symptoms are asked to call their health care providers and not go to emergency departments first. Health officials also encouraged people to avoid touching their eyes, nose and mouth without washing their hands.