Data Notes for the Week of September 30

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If you’re new to the data snapshot, we publish a weekly summary of the status for each of our metrics (you can find past issues on our data and dashboard page). The data below are from September 13—September 26.

Cases decreased during this 14-day period with an average of 143 cases per day.

Last week there was an average of 142 cases per day, but cases were trending upward toward a peak. They are now trending downward off of that peak. The number of people hospitalized with COVID in Dane County hospitals was stable, with an average of 84 people hospitalized with COVID-19 in Dane County hospitals each day. We are not able to discern whether these hospitalizations are among Dane County residents or among patients transferred to the Dane County hospitals from the surrounding areas.* Percent positivity was 3.4% and an average of 4,214 tests were conducted per day. Because percent positivity has been holding steady and has remained under 5%, this is a good indication that we’re testing at the level we need to in order to find cases.

Cases among fully vaccinated people decreased by 33% and cases among not fully vaccinated people decreased by 16% during this 14-day period.

Just over half of the cases were infections after vaccination (breakthroughs), but the age-adjusted rate of cases among not fully vaccinated people was 3.4 times higher than the rate for fully vaccinated people. During this 14-day period, 28% of breakthrough cases and 10% of non-breakthrough cases in Dane County were among people affiliated with UW.

Over the past four weeks, cases increased among children ages 8-11 and adults ages 18-22 and 70-79.

There were 178 total cases among 8-11 year olds during this 14-day period, and 102 of them (57%) were linked to a school or childcare cluster. There were 382 total cases among 18-22 year olds during this 14-day period, and 314 of them (82%) were UW-Madison students.

During this 14-day period, not fully vaccinated youth ages 12-15 had a case rate of 847.1 per 100,000, which was 13.7 times higher than the case rate for fully vaccinated youth ages 12-15, which was 61.6: the lowest rate among all age groups. One unvaccinated child age 12-17 who tested positive in the past four weeks has been hospitalized for COVID. The 7-day statewide average of new hospital admissions for children with confirmed COVID (ages 0-17) is currently at an all-time high, with 8 per day in Wisconsin (from 9/21-9/27). However, we have not seen a local increase in Dane County children being hospitalized.*

*The number of people hospitalized daily in Dane County hospitals is obtained from the EMResource data system. This number can include patients who are not Dane County residents. This data system does not provide identifiable data, so we are unable to discern what proportion of patients are Dane County versus non-Dane County residents, the vaccination status of the people who are hospitalized, or whether each individual is hospitalized for COVID or for something else but happened to test positive for COVID during their hospitalization. Hospitalization data for Dane County residents who have tested positive for COVID is obtained from the Wisconsin Electronic Disease Surveillance System (WEDSS). We learn about hospitalizations either at the time of interview by the case investigator, or when hospitals submit reports to WEDSS to report that someone is hospitalized. Case investigators review each hospitalization report to verify whether the hospitalization was due to COVID-19, and we only mark someone as hospitalized if COVID-19 was the reason for or a contributor to the hospitalization. However, we usually do not receive dates of admission and discharge, so we’re unable to discern what proportion of people hospitalized in Dane County each day are Dane County residents, or the length of stay.