Week 10's COVID-19 Report

Week 10:

Welcome to my Week 10 Report which will provide an update on “Positivity”. These are calculated on a Statewide Basis shown on the posted Table below. It is a simple calculation for the fraction of Tests which come back positive: Positives/Total Tests * 100. . According to a recent NPR Article (5/21, Rob Stein) epidemiologists use Positivity as an indicator for sufficient testing. If the value is above 10%, then officials increase testing capacity. Below 10%, they watch over time how the value changes over time. If the result decreases, then the virus is under control. If not, then it is spreading.

Starting at Week 6, Testing has been expanded all over the state. This past 7 days, we performed a factor of 5 more tests than one month ago. From Week 4 through Week6, the Statewide value for Positivity decreased from 11 to just below 8%. Once Stage 1 of Reopening began, the values began climbing to 14% on Week7 with the latest Positivity Number for the State at 3.9.

The NPR article criticized the CDC sanctioned practice of combining antibody and viral counts and using that total in the calculation. This practice was not suitable for the purposes of calculating positivity: the two tests were based on different chemistry (serological vs swab test), different timeframes (anytime in the past vs. present), and had different a frequency of false negatives.

In response, beginning on May 19, the DSHS has taken antibody tests out of the positivity calculation and has a separate tracking for antibody tests. Several counties have similarly adjusted their testing counts.