DHS Announces Enhanced COVID-19 Data Cleaning Efforts

Data is the tool that drives decisions for public health. And it has been vitally important to inform our decision-making process during the pandemic. As we continue to provide the highest quality, transparent data, today, DHS announces we are ramping up data cleaning efforts as decreasing cases have allowed for increased capacity to focus on data quality.

DHS and local public health agencies have been prioritizing data access to the public as quickly as possible to ensure transparency throughout the pandemic while also performing quality assurance. As declining cases have allowed for increased staff capacity, an enhanced focus on data cleanup is under way. This includes reviewing current and past case and interview data to ensure it is accurate and complete, and duplicate records are merged. Data cleaning efforts also include correcting positive case status from “confirmed” to “probable” if there was a positive antigen result instead of a confirmed PCR result to determine presence of SARS-CoV-2, the virus causing COVID-19. These efforts are similar to routine annual data cleaning efforts that occur for all communicable diseases.

Because of cleanup efforts, data displayed on the website changes over time. In particular, dashboards and data tables that track cumulative cases or deaths, as well as those showing newly reported “net” numbers each day may appear lower than expected – in some counties, substantially lower or even negative. For example, about 3,000 confirmed cases were corrected to probable over the past several weeks, and about 800 non-confirmed cases were corrected to confirmed over the same timeframe, leading to a net decrease of 2,200 confirmed cases. For the purposes of public health follow-up, recommendations for confirmed and probable cases are the same.

Charts showing confirmed cases and deaths by group housing setting are also undergoing quality assurance efforts. This includes matching addresses to long-term care and other congregate living facilities to reduce the number of “unknowns” in our group housing charts. Total numbers of cases and deaths were not impacted by this data cleaning effort. As a result of these additional data quality efforts to compare WEDSS address data with facility addresses, the percent of deaths where group housing setting was unknown decreased from 46% to 26%, and group housing setting data fields are more complete.

For a more accurate picture of COVID-19 over time in Wisconsin, we encourage you to look at the confirmed and probable cases by date of onset or diagnoses (with 7-day averages) and deaths by date of death. Learn more about how COVID-19 cases are tracked and reported.

For up-to-date information about Wisconsin’s COVID-19 response, visit the DHS COVID-19 webpage. Follow @DHSWI on Facebook, Twitter or dhs.wi on Instagram for more information on COVID-19.