Data Notes for the Week of September 17

Today we released this week’s data snapshot. 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 metrics page). We have a few notes for this week’s issue:

Our average number of cases per day hit 170, which is nearly double last week’s average of 94.

Cases per day ranged from 27 to 487 with an average of 170 cases per day. Last week’s average number of cases per day was 94. In this 14-day period there were 2,380 total cases:

• Of all 2,380 cases, 1,298 (55%) were tested by University Health Services, 712 (30%) were tested at community testing sites, and 370 (16%) were tested at other sites, such as health care settings.
• Of all 2,380 cases, 1,385 (58%) were associated with college-aged housing clusters (either live in a dorm or UW student organization housing, live in an apartment complex with 10 or more cases, or live in or are a member of a fraternity or sorority).
• Of 2,202 people fully interviewed so far, 1,460 (66%) identified the likely source of infection as close contact with another lab-confirmed COVID-19 case.
• Of 2,202 people fully interviewed so far, 133 (6%) were associated with a cluster (excluding college-aged housing clusters): 50 from UW sports teams, 22 from health care facilities, 13 from childcare facilities, 12 from workplaces, 8 from congregate facilities, 8 from UW facilities such as dining halls, 7 from restaurants and bars, 5 from weddings, 4 from churches, and 3 from other clusters.
  • Of the 13 cases from childcare facilities, 7 were children and 6 were adults.
  • Of the 12 workplace cases, 2 were from more public-facing workplaces and 10 were less public-facing.

UW-Madison students and staff make up 76% of Dane County cases.

During this 14-day period, 1,808 UW students and 10 staff (1,818 total) tested positive, making up 76% of our total cases, up from 65% last week.

Of the 1,808 UW student cases in this 14-day period:

• 1,298 (71%) were tested by UHS, 399 (22%) were tested at the Alliant Energy Center, and 121 (7%) were tested at other sites.
• 1,764 (97%) were between the ages of 18-22.
• 558 (31%) were linked to dorms, 318 (17%) were linked to fraternities and sororities, and 521 (29%) were linked to apartment complexes on or near campus that have at least 10 or more cases. Note that these are not mutually exclusive: a student could, for example, live in a dorm but also be a member of a fraternity.

As we reported last week, three key strategies are in effect to help slow the spread of the virus. On September 4, we issued quarantine notices to over 400 UW fraternity and sorority members due to outbreaks within their chapter houses. On September 7, UW directed undergraduate students to restrict movement for 14 days, and on September 9, UW shifted to two weeks of remote instruction and placed two residence halls under quarantine. Strategies to restrict movement and reduce contact over fourteen days have been effective in slowing the spread of disease in other communities, but keep in mind we will not see the effects of this intervention immediately given the incubation period of the virus.

The percent positivity metric turned yellow, at 5.2%.

Percent positivity for this period was 5.2%, up from 3% last week. Dane County had increased testing so we expected more cases, but the increase in cases outpaced the increase in testing. This means we know the increase in cases isn't solely from more testing. An increase in percent positivity can indicate more widespread infection, so more testing is needed to capture all cases to ensure that we can provide them with isolation instructions and notify and quarantine their close contacts.

The target for grades 3-5 was not met this week.

The K-12 school metrics are detailed on our website. The Wisconsin Supreme Court issued an injunction that allows K-12 schools in Dane County to fully open for in-person instruction. We are disappointed in this decision and strongly urge all schools to continue voluntary phasing-in of classes for in-person instruction for grades 3-12 per Public Health Madison & Dane County. Our blog post from this week outlines why phased reopening is important.

We will continue to update data weekly and advise schools on their reopening plans. We strongly urge school leadership to continue providing instruction for grades 3-12 virtually.

During this 14-day period, 3% of all cases (78 total) were children ages 0-17.

The lab timeliness and contact tracing metric is red but seems more influenced by lab timeliness.

Lab timeliness (how quickly labs are reported to us) and contact tracing (how quickly we can reach out to cases) are combined into one metric because lab timeliness directly affects contact tracing. During this period 52% of cases were contacted by public health within 48 hours of being tested, compared to 55% from our last snapshot. From September 1 to September 14, it took an average of 1.3 days to receive a lab result, which only gives our contact tracers a few hours to reach a person who tested positive in order to meet the 48-hour goal of this metric. The percent of lab results returned in 24 hours has decreased over the last several weeks. This may indicate that increased volume of tests to process are impacting lab timeliness.

For the 13th week in a row, Dane County is classified as “high activity level” on the Wisconsin Department of Health Services (DHS) COVID-19 Activity Level Tracker.

Our Forward Dane metric for cases (see the first section of this blog) accounts for burden but not trajectory. The DHS metric combines the burden of cases over a two-week period (number of cases per 100,000 residents) and the trajectory, which measures the percent change in cases from the previous week to the current week and whether that change is statistically significant.

As of the DHS update on 9/16/20, Dane County has a high burden of 458 cases per 100,000 residents, and a growing trajectory in the number of cases from the most recent 7-day period compared to the prior 7-day period. This puts us at a high activity level. We want to reduce our activity level in order to better control the spread of COVID-19 in our community.

Select data dashboard metrics are now available for download.

Each week on Thursdays we will upload a new Excel file with select metrics from the data dashboard. You can also find this file at the top of our Data & Metrics page.