COVID-19 transmission increasing in western Washington, rates flat but higher in eastern Washington

October 14, 2020

Report findings include:

  • Transmission is increasing in western Washington and recently plateauing in eastern Washington. The best estimates of the reproductive number (how many new people each COVID-19 patient will infect) were 1.12 in western Washington and 0.94 in eastern Washington as of September 27. The goal is a number well below one, which would mean COVID-19 transmission is declining.
  • The situation in eastern Washington is unstable and efforts to control the spread of the virus must be strictly maintained or intensified to avoid a backslide. This instability is clear in case and hospitalization numbers, where we’ve seen increases and decreases at various points in September rather than the desired steady downward trend. The proportion of positive tests to total tests also remains high. Per person, the case rate in eastern Washington is twice as high as in western Washington and the daily hospitalization rate is more than twice as high.
  • Case counts in western Washington are increasing across all age groups and over broad geographic areas. This suggests increases are due to broad community spread, not driven by a single type of activity or setting. Though all age groups are seeing increases, the rising trends among older people are particularly concerning because these groups tend to experience more severe illness.
  • Recent growth in cases is widely distributed across a number of counties. Some larger counties (Clark, King, Kitsap, Pierce, Snohomish and Thurston) are seeing steady increases. Several smaller counties (Lewis, Mason, Pend Oreille and Skagit) are clearly experiencing increases, though the total number of recent cases remains low. Benton and Franklin counties are seeing gradual but steady increases as well.
  • Trends are also mixed in counties with flat or decreasing case counts. In Spokane County, the steep increase in cases in early to mid-September may have reached a plateau. Case counts are fluctuating in Whitman County, with some likely increases in older people following a recent spike in the college-age population. Cases remain flat in Yakima County. Grant and Grays Harbor counties are seeing steady declines, and Whatcom County is starting to see decreases as of the start of October.

“As COVID-19 activity intensifies, it’s incredibly important that we all take precautions to reduce the impact of seasonal changes like spending more time indoors,” said Secretary of Health John Wiesman. “We must be especially careful to avoid gathering in groups inside, including with family and friends outside of our immediate household. That includes limiting group size, gathering outside or improving ventilation inside, cleaning and washing hands frequently, wearing face coverings (including inside our homes) and staying over six feet apart.”

DOH partners with the Institute for Disease Modeling, Fred Hutchinson Cancer Research Center, University of Washington and the Microsoft AI for Health program to develop these reports. New reports will be published every other week and as needed when there are major changes in trends.