MADISON (WKOW) -- Public Health Madison and Dane County addressed Friday its struggle to process a backlog of negative COVID-19 test results, skewing its reported infection rates.
According to DHS secratary Andrea Palm, this was a problem plaguing many municipalities across the state.
"As they prioritized those positive cases, negative cases are dragging behind a day or two or even three as they are making sure they're focusing on stopping the spread,"she said.
In a massive update, the online data dashboard public health maintains added around 17,000 negative test results adjusting the positive rate from the past week down to 2.1 percent.
The percent positive rate measures how many COVID-19 tests have returned with positive results. Expressing the returns as a percentage helps account for if an increase in new cases is due to more testing or greater spread.
Public health uses the percent positive rate as one of its metrics in the Forward Dane reopening plan governing how and when certain social distancing measures, including many imposed on businesses, can be relaxed or eliminated.
Acknowledging the issue, public health suspended calculating its metrics concerning percent positive results and total tests conducted this week.
"Over the past couple of weeks, our data dashboard has appeared to have a high percent positivity rate," public health said in a Facebook post. "This is because each negative test has to be processed manually by a staff person. Our staff prioritize processing positive results, and as the amount of testing has increased, we have had a backlog of negative tests to process."
In the past several weeks, it had not been uncommon for Dane County's percent positive rate for the most recent day to begin in the double digits and then slowly adjust lower as time passed and the county processed more negative tests.
The numbers on the data dashboard gave the impression that the county was continuously seeing greater spread of COVID-19.
The most current data displayed Friday morning was for July 18. The numbers showed a 6.1 percent daily positive rate and a weekly average of 13.4 percent. By Friday afternoon, following the addition of the new negatives, July 18's daily rate was down to 2.1 percent and the weekly rate at that point was under four percent.
Dane County, according to the now up-to-date dashboard, did see a sharp increase in COVID-19 cases beginning in late June. However, that rate began to subside as the weeks progressed.