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Since January 21, 2020, Public Health – Seattle & King County has responded to an outbreak of novel coronavirus (COVID-19) in coordination with our partners at the Washington State Department of Health (DOH) and the Centers for Disease Control and Prevention (CDC). Timely and accurate local data are one of the cornerstones of our COVID-19 response, helping us inform policy decisions and identify communities most directly impacted by virus.

Data sources

  • COVID-19 outcomes and immunizations data are from the Washington Department of Health.
  • Population estimates come from the 2020 Office of Financial Management and American Community Survey.

Reporting delays and limitations

Due to reporting delays (data lags), data is preliminary and subject to change. Data will be refreshed retrospectively with ongoing data quality improvements.

Please also note that the data reflect reports for King County residents received through midnight the day before. Due to reporting delays, the following are considered incomplete and are excluded from our reports:

  • Cases: 3 most recent days
  • Hospitalizations: 4 most recent days
  • Deaths: 5 most recent days
  • PCR test counts and percent positivity: 7 most recent days

Data on testing volume and percent positivity have a larger reporting delay because some laboratories report results using processes that are not fully automated. There is also substantial underreporting of antigen and point-of-care test results, such as rapid tests for diagnosing COVID-19 conducted by facilities other than laboratories. Because of these issues, it is not possible to identify how many antigen and point-of-care tests are performed on any given day.

Hospitalizations and death data

Hospitalizations and deaths are counted for individuals where the outcome was due to COVID-19 illness or were COVID-19 related. Hospitalization counts for recent days may include incidental COVID-19 hospitalizations (hospitalizations for injury or illness not primarily related to COVID-19). All hospitalizations are reviewed by our Disease Research Intervention Specialists and incidental hospitalizations are excluded. Counts on Mondays may include higher numbers of hospitalizations because review is not conducted over the weekend.

Deaths among persons with COVID-19 are investigated by our Disease Research Intervention Specialists to determine if the cause of death was confirmed or suspected to have been related to COVID-19. Death investigations are conducted by reviewing the decedent's death certificate and, when necessary, medical record information. If COVID-19 is ruled out as a cause of death, these deaths will be removed from our dashboards and reports. Death certificates are typically filed within 2 weeks of the date of death; however, those can take up to a year to be finalized. Our team conducts death investigations as decedents are identified and information becomes available, which can be some time after COVID-19 infection and death.

Average rates

The 7-day average rate is used to adjust for daily variations, which may be large among smaller populations. It is determined by first calculating the 7-day rate for each day in the past 28 days. Then, the average of the 7-day rates for the past 28 days is taken.

COVID-19 Community Levels versus Community Transmission

COVID-19 Community Levels are categories set by the CDC to determine the impact of COVID-19 on communities and actions to take. The CDC also provides Transmission Levels (also known as Community Transmission) to describe the amount of COVID-19 spread within each county.

The COVID-19 Community Level reported on the Current COVID-19 Metrics webpage may differ from what is reported on the CDC web page for several different reasons, including: (a) the Current COVID-19 Metrics web page uses the new COVID-19 admission rate and the percent of staffed inpatient beds occupied by COVID-19 patients for only King County, while the CDC web page uses these metrics for the Health Service Area (which includes other neighboring counties); (b) the new COVID-19 admissions rate on the Current COVID-19 Metrics web page excludes cases among people who are hospitalized for other reasons but also have COVID-19 (‘'Incidental COVID-19 hospitalizations”), while the CDC web page includes these hospitalizations; (c) this web page is updated Wednesdays while the CDC web page is updated on Thursday.

Age standardization

Our estimated rates for demographic categories are age standardized. Age standardization, sometimes referred to as age adjustment, is a common statistical technique used in public health data that accounts for differences in the age profiles between races and ethnicities, and between sexes, which allows for a more representative comparison. Learn more about age standardization.

Race and ethnicity

We calculate estimated rates for race and ethnicity. Individuals of Hispanic/Latina/o/x ethnicity, race/ethnicity are categorized as "Hispanic", while non-Hispanic/Latina/o/x ethnicity individuals are categorized as the race they selected. Individuals who selected multiple races are categorized as "multi-racial".

Sex and gender

The data on sex is representative of sex assigned at birth. Non-binary and gender diverse data are presented where available and is dependent of the data source. While we calculate rates for some sex and gender categories, we do not have population estimates – and therefore rates – for those who identify as non-binary.

More details

Additional data notes are included on data dashboards.

More details on data definitions can be found on the Download the data page.