Data Notes for the Week of July 20
Posted on Monday, Jul. 20, 2020 at 4:57 pm
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 went down from last snapshot, which is the first time this has happened since May 18.
The number of cases per day metric was red in the last data snapshot, and it remained red during this 14-day period. Cases per day ranged from 40 to 120, with an average of 80 cases per day, down from 98 in the last snapshot.
From July 4 through July 17, 1,122 people tested positive for COVID-19 in Dane County. As of this morning, 846 have had complete interviews. Here’s what we know about these cases:
- Of all 1,122 cases, 633 (56%) were tested at community testing sites (606 at the Alliant Energy Center).
- Of all 1,122 cases, 437 (39%) were young adults between the ages of 18-25.
- Of 846 people who have been fully interviewed so far, 342 (40%) reported attending a gathering or party with people outside of their household.
- Of 846 people fully interviewed so far, 117 (14%) were associated with a cluster: 41 from workplaces, 34 from bars and restaurants, 14 from college-aged housing (including sororities, fraternities, near-campus apartments), 8 from congregate facilities, 7 from gyms, 7 from childcare facilities, 2 from salons, and 4 from other clusters.
There are signs the rate of spread may be decreasing.
The “R” number estimates the rate of spread of a disease in a community. It represents the number of people who will be infected by a single individual who has an infection. For Dane County, R is calculated using a calculator produced by researchers at the London School of Hygiene and Tropical Medicine. The R number on June 27 was 1.51, the highest of the epidemic. On July 17, it was 0.93. CDC considers:
- An R of 0.33 a “rapid decrease”
- An R of 0.8 a “slow decrease”
- An R of 1.2 a “slow increase”
- An R of 1.8 a “rapid increase”
We continue to see racial and ethnic disparities in cases and hospitalizations. Young people 20-29 continue to be the age group with the most cases.
Hispanic or Latinx people who tested positive made up 17% of cases and 10% of hospitalizations while accounting for just 6% of the population, and Black people made up 13% of cases and 23% of hospitalizations, and account for 6% of the population.
People in the 20-29 age group made up the greatest proportion of cases: 41% of cases were in this age group; the next largest was age 30-39 at 14% of cases.
Percent positivity and number of tests this period were not updated this week. Positive tests continue to be processed within 24 hours.
Due to a backlog of negative tests in our data system that need processing, we are not calculating the percent positive and number of tests metrics this week.
When someone tests negative, they receive notification from the facility where they got tested on their test result. That test information enters our data system, and we have staff who process the test by verifying the result and matching it to the person who was tested if they already have a record in our data system.
We always process positive results within 24 hours so those people can be assigned a case investigator. Due to record numbers of both cases and tests over the past month, we only have negative tests fully processed through July 10. Notification of positive and negative results happens in a timely fashion. The administrative processing of the negative results is what is delayed. We have recently hired additional staff to help process these tests.
The lab timeliness and contact tracing metric is still red.
As we reported last week, lab timeliness and contact tracing are combined into one metric because we can only start tracing once we receive a lab report (see timeline below). The metric remained red.
Tying together the measures of lab processing time and time to contact positive cases gives us insight into how quickly we can isolate infection and stop it from spreading. Keep in mind this metric is asking a lot of our lab, healthcare, and public health systems, and this is a very ambitious metric. All of this has to happen in 48 hours:
- Someone has to be tested
- The sample has to be transported to the lab
- The lab has to test the sample
- The lab has to input the results in the state database
- Our team has to collect and process the result
- Our team has to call the person who tested positive
- The person who tested positive has to answer their phone when we call
For this metric to turn green, that all needs to happen within 48 hours for 85% of cases. We currently have 75 people conducting contact tracing, and 26 people supporting contact tracing work, and we are continuing to expand capabilities by hiring more.