Did I make the current level of novel coronavirus infections in King County sound worse than it is?
In my previous column, I looked at cumulative data from Public Health — Seattle & King County, going back to the first days of the pandemic here. It showed that more than 5% of the tests for COVID-19 came back positive.
The idea was to gauge the overall impact of the virus in King County, and to illustrate the degree to which that impact has varied from place to place.
But a number of readers, analyzing the public-health data themselves, pointed out to me that the rate in King County has been quite a bit lower than 5% in recent weeks. And, as I mentioned in my column, the World Health Organization recommends a positive-test rate of 5% or lower over a two-week period before reopening is advisable. As some readers noted, we have achieved that.
“In recent weeks the positivity rate for King County as a whole has been less than 4 percent … Seattle’s positivity rate is even lower,” one reader emailed. “The drop in positivity rate in King County (with the rise in other counties, like Okonogan [sic] County), and the low positivity rates in Seattle (with high testing), is a story worth telling, particularly with the Seattle school district on the cusp of closing in-person school this fall. “
Indeed, the data from July 13 to 27 shows that in total, about 65,000 tests were administered for COVID-19 in King County, and 2,500 had a positive result — that’s 3.9%.
About 30,000 of those tests were administered within the city of Seattle, and fewer than 600 were positive — that’s just 2%.
Those numbers are certainly better than the cumulative ones I reported on last week. But what the averages for the county and Seattle don’t show you is that there is tremendous amount of variation from place to place, and the positive-test rate is still alarmingly high in some parts of 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.
South King County remains a coronavirus hot spot. Positive-test rates in the Auburn South HRA in particular are especially high. In the two-week period, 92 people were positive for COVID-19 out of the 703 who were tested, for a rate of 13.1%. The small city of Algona is located within the Auburn South HRA, and the positive-test rate here was almost 18%.
The highest rates are all nearby, in areas such as Kent, Federal Way, Tukwila and SeaTac.
Of all the HRAs, Vashon Island has had the lowest rate of positive tests since the epidemic began. And that trend holds true for the July 13 to27 period. Vashon had one confirmed case of COVID-19 out of 234 tests, for a rate of 0.4%.
Two other HRAs had a positive test rate below 1%, and both are in Seattle: Queen Anne/Magnolia and Ballard were both at 0.9%.
While every HRA had at least one confirmed case of coronavirus in this two-week period, there were four small King County cities with zero positive tests: Hunts Point, Mirrormont, Riverbend and Skykomish.
Most parts of Seattle were below the King County average positive-test rate of 3.9% in the two-week period, but not all. The Southeast Seattle HRA was at 4.6% and the Delridge HRA in West Seattle was at 4.3%.
We see higher rates of positive tests in areas of the county that have a greater share of low-income households that may have less access to health care. People in these areas aren’t as likely to get tested if they’re experiencing milder symptoms compared with people in more affluent areas. And when a higher percentage of the people getting tested are very sick, a higher percentage of the tests are likely to come back positive.
A higher rate of positive tests can also simply mean that there’s a higher level of the virus in that community.
Sadly, 39 people died from COVID-19 in King County in the two-week period. The HRA with the most deaths was Auburn South, with five.
But the city of Kent, which is split up into three HRAs, also had five deaths. There are four HRAs located within the city of Bellevue, which had three deaths.
In the 13 HRAs that make up the city of Seattle, a total of 12 people were lost to COVID-19 in the two-week period.