Seattle-area residents have been dealing with the COVID-19 epidemic longer than anyone else in the country. The first confirmed case in the U.S. was in Snohomish County on Jan. 20. Then in February, with an outbreak of the virus at Kirkland’s Life Care Center nursing home, we became the nation’s first COVID-19 epicenter.

But the impact of the virus in King County has been felt differently from place to place. Data collected from the beginning of the epidemic by Public Health — Seattle & King County shows that the percentage of positive tests, and the rates of testing and death from COVID-19 vary tremendously across the county.

The data is reported for 48 Health Reporting Areas (HRA). These can be as small as neighborhoods or they can cut across cities and towns in less populated areas of the county.

Communities in South King County show the highest rate of positive tests for COVID-19. As of July 22, in the southern half of Auburn, 12% of the tests administered came back positive — that’s more than 300 confirmed cases out of about 2,600 people who’ve been tested.

Other areas south of Seattle with very high rates of positive tests are SeaTac, Tukwila, Kent, North Highline and Federal Way. In all these places, at least one in 10 people who’ve been tested for COVID-19 had a positive result.

South King County has a higher percentage of lower-income households than Seattle or the Eastside, and that helps explain the high rate of positive tests. In places where people have less access to health care, you will find a higher rate of positive tests, said Sharon Bogan of Public Health — Seattle & King County, in an email.

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“Higher positivity means a larger proportion of the people tested are ill and less severe cases are not being tested,” said Sharon Bogan of Public Health — Seattle & King County, in an email. “This can be because testing capacity is not adequate to test people with less severe symptoms, or people with less severe symptoms don’t seek testing.”

A higher percentage of positive tests can also mean simply that there is a higher level of the virus in a community. South King County residents are more likely to work in service jobs, meaning they interact with the public and have a greater chance of catching the virus. This area is also the most diverse part of King County, and Hispanic and Black people have a higher rate of COVID-19 infection.

The areas with the lowest rates of positive tests are wealthier and whiter. On Vashon Island, less than 1% of tests have come back positive. There have only been seven confirmed cases on Vashon, out of more than 1,100 people tested.

The other areas with the lowest percentage of positive tests are in Seattle: Fremont/Green Lake, Ballard and Capitol Hill/Eastlake, all around 2%.

In May, the World Health Organization said the positivity rate should be at or below 5% for a 14-day period before reopening is advisable. As of July 22, King County’s positivity rate was 5.3%. Washington state’s goal is 2%.

One factor influencing positivity rates is the number of tests performed. And, far and away, Seattle city residents are more likely to get tested for COVID-19 than people from other parts of the county.

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The highest rates of testing are in central Seattle. In the downtown neighborhoods, residents have been tested at a rate of more than 18,000 per 100,000 people. Capitol Hill/Eastlake is very close behind.

The nine areas with the highest rates of testing are all within Seattle city limits. Mercer Island ranks 10th.

“Rates of testing correspond to access to testing — how available testing is across communities, how common COVID-19 is in the community, and health care seeking behaviors,” Bogan said. “For example, there may be differences in how likely someone is to go and get a test if they are experiencing mild symptoms as well as factors such as trust of the health care system.”

(Jennifer Luxton / The Seattle Times)

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The areas at the other end of the spectrum from Seattle are the suburban and exurban areas to the east. The lowest rate is in the Bear Creek/Carnation/Duvall HRA, with only about 7,400 tests per 100,000 population. Sammamish and central Bellevue are just a little higher.

“If there are fewer options for testing, fewer ill people, or lower health care seeking behavior,” Bogan said, “we are likely to see a lower rate of testing.”

The rate of death also varies greatly. It is highest in communities with nursing homes and older populations, people who are very vulnerable to severe symptoms with COVID-19.

The highest rate of death is in Shoreline, which has several nursing homes where people have tested positive for the virus. There have been 60 deaths in Shoreline, which pencils out to a rate of about 108 deaths per 100,000 residents. Issaquah has the next highest rate, followed by Kirkland, where the virus claimed its first victim in the U.S.

Of the 48 HRAs in King County, there is only one without a single fatality due to COVID-19 so far: Vashon Island.