Today’s report on COVID-19 in King County | Tue Apr 21

Today in public health updates, Seattle & King County Public Health outlines the current knowledge surrounding antibody (serology) testing.  There is clearly important value in understanding true individual immunity as well as the level of immunity to COVID-19 across the population.  But with the science on COVID-19 still emerging, there is still a lot we need to learn about how well antibody tests can help answer these questions.  For the full article and report, visit the Public Health Insider.   

Otherwise, this daily synthesis of the Public Health data is provided by Will Daugherty of Pacific Science Center.  Thanks Will!

Public Health has updated the data dashboard.  As of 11:59 pm yesterday, April 20, there were 5,379 confirmed cases of COVID-19 in King County, 86 more than the previous day.  There have been 372 confirmed deaths in King County due to COVID-19, 6.9% of all confirmed cases.

The numbers that Public Health reports each day include delayed results from previous days.


The first graph below shows new cases (blue bars) and the 7-day average (red line).  Of the 86 new cases reported today, 57 were confirmed yesterday and the remaining 29 were confirmed in previous days but reported to Public Health in the last day, resulting in upward revisions of the totals for previous days.  The 7-day average has been in decline since April 1, but the downward trajectory is becoming elongated.  The trailing 7-day average is 97 new cases per day.  This is the same level that it was March 21-22, right before Governor Inslee issued the “Stay Home, Stay Healthy” order on March 23.

The second graph below shows the total case count.  With 5,379 total cases as of 11:59 pm yesterday, the compound daily growth rate during the last 7 days has been 2.0%, less than the 3.0% rate during the prior 7 days.  At a 2.0% compound daily growth rate, the number of cases doubles every 35.8 days.  One week ago, cases were doubling every 23.4 days.  Two weeks ago, cases were doubling every 13.4 days. Three weeks ago, cases were doubling every 7.4 days.

The third graph below shows the trajectory of cases in King County with the total number of cases on the horizontal axis and the new cases on the vertical axis.  Each axis is on a logarithmic scale.  Each blue dot represents a daily report.  The dot farthest to the left is the February 28 report.  Time passes from left to right as the total case count grows.  The dot farthest to the right is today’s daily report.  We can see a clear change in the trajectory since March 28, shortly after Governor Inslee’s “Stay Home, Stay Healthy” order on March 23.

Will Daugherty welcomes your questions and comments.  His email is