Welcome to our first COVID-19 Weekend Update. Intended to supplement our daily weekday reports, the Weekend Update provides details on where infected individuals contracted the virus, numbers of tests administered, and positive vs. negative testing results in Snohomish County.

Testing, along with contact tracing, has been identified as a key weapon in the battle with COVID-19 both internationally and locally. Knowing where the cases are is the first step; then through contact tracing individuals who come in close contact with known infected individuals can also be identified, tested and, if necessary, asked to quarantine.

Weekly test numbers are presented in two ways: broken out by week (red and green bars), and cumulative over the full reporting period (yellow and green bars). The weekly numbers chart shows a steady rate of testing, with between 2,500 and 3,500 tests administered countywide each week. Notably, the proportion of positive results has been decreasing steadily over the reporting period.  The cumulative testing chart reflects this, showing steady growth in the pool of tested individuals and a predominance of negative results.

To date, 29,530 tests have been conducted in Snohomish County (3.59% of the total population of 822,083), of which 97.01% (26,829) were negative and 2.99% (2,791) were positive. For comparison, the latest data on statewide testing from the Washington State Department of Health COVID-19 Information website reports 308,358 Washingtonians have been tested to date (3.95% of the total population of 7.8 million), of which 93% (289,093) were negative and 6%  (19,265) positive.

The Source of Exposure chart displays the history over the past two weeks on how Snohomish County COVID victims acquired the virus. According to these data, community transmission (going to stores, gathering in groups, touching surfaces containing virus particles, failing to maintain recommended social distancing, etc.) is the overwhelming method of infection. The next most prevalent source is long-term care facilities, which primary affects seniors.

Taking a closer look at this population, the Local Long-term Care Facilities chart focuses on test results at facilities in our coverage area, breaking these out by residents and staff and providing both actual numbers and percent positive results.  The relatively high number of cases at Edmonds’ Rosewood Courte came as a result of intensive testing conducted on April 13; additional details and statements from Rosewood Courte officials are available in our Daily COVID Report from April 15.

— By Larry Vogel