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COVID-19 In King County WA – April 27 Report

by | Apr 27, 2020

Update from Public Health – Seattle & King County

Public Health has updated the data dashboard. As of 11:59 p.m. yesterday, April 26, there were 5,990 confirmed cases of COVID-19 in King County, 78 more than the previous day. There have been 416 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.

Today’s update from Public Health includes this:

A new report details how social distancing measures have reduced transmission of COVID-19 in King County to the point where new cases are expected to slowly decline or plateau at current levels. Additional interventions to further cut transmissions should be in place before social distancing measures could be relaxed to avoid risk to public health.

Modeling from the Institute for Disease Modeling (IDM) show the effective reproductive number – the number of new cases stemming from each COVID-19 infection – has declined from around 3 in early March to near 1 through April 4. This is consistent with previous estimates since the statewide Stay Home, Stay Healthy order went into effect on March 23.

“We’ve done a very good job in King County suppressing transmission of COVID-19 and that’s largely due to the great work of our community in staying home and distancing to the extent possible,” said Dr. Jeff Duchin, Health Officer for Public Health – Seattle & King County. “However, we still have way too many cases occurring each day. That means we’re vulnerable to a rebound that could potentially overwhelm our healthcare system if we prematurely ease up on our distancing steps.”

Projecting forward, if distancing measures were lifted starting May 1, IDM’s new model predicts a rapid rise in the rate of cases that would likely exceed recent peak levels by the end of the month.

In contrast, if new strategies are added on top of current distancing measures — such as a significant increases in testing for COVID-19, and detailed contact tracing of those who have contracted COVID-19—the model suggests the effective reproductive number would drop further and the number of cases would go down more quickly.

Until then, the report suggests, disease transmission will remain extremely sensitive to policy choices and community behavior.

Observations

The first graph at the top of this post shows new cases (blue bars) and the 7-day average (red line). Of the 78 new cases reported today, 67 were confirmed yesterday and the remaining 11 were confirmed in previous days but reported to Public Health in the last day, resulting in restatements of the totals for previous days. The 7-day average has been in decline since April 1. The trailing 7-day average is 86 new cases per day, just below where it was (87) on March 20. This is what Dr. Duchin is referring to when he says “we still have way too many cases occurring each day.”

The second graph below shows the total case count. With 5,990 total cases as of 11:59 pm yesterday, the compound daily growth rate during the last 7 days has been 1.5%, less than the 2.2% rate during the prior 7 days. At a 1.5% compound daily growth rate, the number of cases doubles every 45.6 days. One week ago, cases were doubling every 32.2 days. Two weeks ago, cases were doubling every 22.0 days. Three weeks ago, cases were doubling every 12.2 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.

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