Technical Notes
Time delays and lags
Minor time delays in the collection of laboratory testing data, confirming cases, hospitalizations, and deaths occur regularly due to processing and reporting variation between data sources. This variation is due to differences in individual actions, laboratory capacities, and case confirmation and reporting processes.
After analyzing time lags between steps, the Washington State Department of Health (DOH) increased the period of incomplete reporting for most metrics to 10 days to ensure that 90% of data are accounted for in our posted numbers. For each metric shown on a time trend, the incomplete data period is shown in light gray. We provide a Learn More link with more detail on the period of incomplete data.
Number of infections
Public health experts agree that the true number of people who have been infected with COVID-19 in Washington greatly exceeds those that have been laboratory-confirmed. It is very difficult to know exactly how many people in Washington have been infected to date, since most people with COVID-19 experience mild illness and testing is still not widely available.
Cases
Effective June 16, 2020, cases are added to the DOH dashboard according to the date a person’s first positive COVID-19 laboratory test result was entered into the Washington Disease Reporting System. Previously, the date a case was reported to DOH was used as the case date. Our current approach provides a more accurate designation of case confirmation dates while shifting less than 10% of case counts by date, most noticeably for cumulative case counts and graphics.
Testing
Two important data issues continue to affect results presented on the testing tab: 1) the delayed entry of negative lab results into our data system; and 2) the lack of an assigned county for about 21% of negative test results. These issues impact some counties disproportionately. Washington State Department of Health (DOH) continues to work on a sustainable solution.
Effective August 25, 2020, DOH changed the methodology for reporting test results. The total number of tests are now reported instead of the total number of individuals tested. New positive and negative test counts include all molecular tests (by specimen collection date) of individuals who have not previously tested positive. Multiple test results from the same day are counted only once and we exclude repeat tests on an individual after the first positive result. This methodology has been applied to the entire dashboard timeframe. The changes in our testing methodology did not affect dashboard testing trends.
Deaths
Deaths are reported to the state by health care providers, medical examiners/coroners, local health departments, and others. For this reason, the statewide count of deaths often lags behind the counts of local health departments.
As of December 10, 2020, death counts on our dashboard reflect those in our official vital records database (the Washington Health and Life Events System) where the cause of death was confirmed or suspected to have been COVID-19. If COVID-19 is later ruled out as the official cause of death, we will remove these deaths from our dashboard. We no longer report preliminary death information recorded in other systems.
DOH updates COVID-19 death data on normal working days, Monday-Friday and adds the counts collected on weekends to the following Monday and Tuesday reports.