SEATTLE — COVID-19 transmission is increasing in western Washington and has recently plateaued in some areas eastern Washington, according to the latest data released by the Washington Department of Health (DOH) Wednesday.
The recent increase in western Washington could be due to the changing weather conditions, according to the report. The data analyzed COVID-19 tests and cases through Oct. 2.
The data shows the estimated reproductive number, meaning how many new people each COVID-19 patient will infect, was 1.12 in western Washington and 0.94 in eastern Washington as of Sept. 27. The goal is to have that number be "well below" one, which would mean COVID-19 transmission is declining.
In western Washington, the seven-day rolling average of COVID-19 case counts increased from a recent low of 194 on Sept. 12 to 307 on Oct. 2, the DOH said in its report. On the other side of the state, the seven-day rolling average decreased from a recent high of 203 COVID-19 cases on Sept. 24 to 181 on Oct. 2.
Although cases appear to be declining, the DOH said eastern Washington remains in an unstable position where any lapses in behaviors to reduce transmission, such as mask wearing and social distancing, could rapidly reverse decreasing trends in cases and increase COVID-19 mortality.
In western Washington, the DOH said COVID-19 cases have been increasing in all age groups since mid-September, meaning there's no single transmission route that's driving rising trends.
In fact, the data shows the majority of cases in the state are not known to be linked to high-profile outbreaks, such as those at the University of Washington or Washington State University.
Several of Washington state's larger counties, including Clark, King, Kitsap, Pierce, Snohomish and Thurston, experienced steady increases in COVID-19 cases through Oct. 2. In Spokane County, there was a steep increase in cases over the three weeks to Sept. 24, but it may have reached a plateau, according to the DOH.
In regard to increasing cases in western Washington, the DOH said it's possible we're seeing the beginnings of a seasonal effect due to people gathering indoors more often as the weather turns colder and wetter outside.
“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 in a statement. “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.”
As of Oct. 12, there are 94,775 confirmed COVID-19 cases in Washington state, including 2,211 deaths. More than two million people have been tested for COVID-19 in the state, according to the DOH COVID-19 dashboard.