COVID-19 Forecast for El Paso County — Sept. 21

Plus, our resident microbiologist on the outbreak at the University of Colorado at Boulder

Good morning, and happy Monday. On this pre-pandemic date last year, Colorado Springs residents were enjoying the first day of the Pikes Peak Regional Airshow. (Organizers have not scheduled a 2020 event.) 

Today, Phoebe Lostroh returns to give her weekly COVID-19 forecast for El Paso County and to explain the COVID-19 caseload at the University of Colorado at Boulder. Lostroh is a professor of molecular biology at Colorado College on scholarly leave who is serving as the program director in Genetic Mechanisms, Molecular and Cellular Biosciences at the National Science Foundation.

➡️ICYMI: On Wednesday, we talked to CC’s COVID-19 Emergency Manager and some students about some of the bumps during the South and Mathias Hall quarantines. We also recapped the Town Hall on Housing.  

Phoebe’s Forecasts

NOTES: These forecasts represent her own opinion and not necessarily those of the National Science Foundation or Colorado College. She used the public El Paso County dashboard for all data. Lostroh prepared these forecasts on Sept. 18. 

⚖️ How her predictions last week shaped up: Sept. 19 is the last day of Morbidity and Mortality Weekly Report week 38 in the national public health calendar. It is the 28th week since the first case was detected in El Paso County. Since March 13, 168 El Paso County residents have died of COVID-19. Last week, Lostroh predicted between 6,397 and 6,541 cumulative reported cases as of Sept. 17, and in actuality, there were 6,629. Her prediction was an underestimate, as the number of reported cases has taken a turn. Instead of cases reported each week decreasing, they have almost doubled compared with the number of cases last week. 

It usually takes 3–4 weeks for changes in behavior to show up in the record of reported cases. Lostroh suspects the relevant changes that started 3–4 weeks ago are from extending the last call at bars to 11 p.m. and some K–12 schools beginning in-person instruction. 

Predicted cumulative reported cases in El Paso County

🗝️ Key points: Lostroh thinks we will probably see a total number of cases somewhere between the exponential curve fit for the recent data and the “worst case” exponential curve fit to the two weeks prior to the mask order in July. She’s leaning toward the more pessimistic end of the range of 6,993–7,090 total reported cases as of Sept. 24. On the other hand, the local percent positivity is below 3%, which might keep El Paso County closer to the lower end of that range. There is no separate “best case” forecast because El Paso County’s cases are increasing, so the linear calculation is the most optimistic prediction.

Reported cases by week

🗝️ Key points: The graph shows when various measures to loosen restrictions started (green arrowheads) and when measures to slow spread started (yellow arrowheads). Lostroh also marked events that might increase social mixing indoors with green arrowheads. Until now, El Paso County had seven weeks of declining cases, but this week there has been an abrupt reversal. The total reported cases this week is almost as high as it was three weeks ago. This reversal occurs three weeks after Democratic Governor Jared Polis changed the last call for alcohol at bars from 10 p.m. to 11 p.m., which is consistent with an increase in social mixing indoors and thus an increased risk of spreading or acquiring COVID-19. It’s probably too early to tell whether Labor Day and/or the cold snap El Paso County had right after Labor Day will have a similar effect. 

K-12 school guidance for El Paso County

🗝️ Key points: The Harvard University Global Health Institute suggested the thresholds Lostroh uses in this forecast. El Paso County has been in the yellow zone for almost six weeks. Lostroh expects El Paso County to stay in the yellow zone for two more weeks, meaning that grades K-8 are safe to meet in person if pandemic-resilient buildings, classrooms, and practices are in place. If El Paso County crosses into the orange zone, only grades K-5 should meet in person. For the past few weeks, El Paso County was headed for the green zone, which is when all classes could meet in person, but unfortunately the trend has reversed.

14-day incidence annotated with the state’s viral spread thresholds

🗝️ Key points: El Paso County exceeded the “high viral spread” threshold months ago and failed to cross into the medium spread zone this week. Instead, it looks like the downward trend has reversed, and Lostroh predicts El Paso County can expect two more weeks in the “high viral spread” zone. The county might cross back into “very high viral spread” after that unless El Paso County implements additional public health measures, according to Lostroh. 

Total nose-swab tests reported and rolling percent positivity

🗝️ Key points: The total tests reported in 14 days are plotted in pink using the left-hand axis, while the percent positivity in those 14 days is plotted on the right-hand axis in blue. El Paso County has been beneath the important 5% positivity threshold for almost six weeks. The trend in percent positivity is more optimistic than the trend in newly-reported cases, but so far in the local epidemic, the predictions based on the reported cases have been more accurate than ones based on percent positivity. El Paso County calculates percent positivity using 14 days of data, which Lostroh also does; this means the data going into any point include data that were reported two weeks ago. It could be that in a fast-changing situation, this method of calculation gives more optimistic results. But because the data are provided on the day the test results are reported to the county, rather than the day that the test was administered, shorter averages are not necessarily any more informative. Even the percentage for any single day represents percent positivity in the community two to five days ago. 

Dr. Deborah Birx told the American Society for Microbiology to watch for an inflection around 5% positivity on the county level as a warning signal that the cases are going to go up substantially in a couple of weeks, which is what happened to El Paso County the last time cases surged. El Paso County saw a percent positivity higher than five from May 26–June 7 and then a strong surge in 14-day incidence from June 16–July 28.

Q-and-A with Lostroh: Our resident microbiologist on the controversial CDC guidelines for testing asymptomatic cases

This interview has been edited for length and clarity.

CC COVID-19 Reporting Project: The Centers for Disease Control and Prevention has been in the news a lot lately about publishing a controversial guideline. What happened, and why is it such a big deal? 

Lostroh: The CDC made this weird change a little while ago — I can’t remember how many months ago at this point — where they said they no longer recommended testing people who had been exposed to known cases unless their doctor recommended it. Well, this is the opposite of all good health, and it was one of the main reasons that county health departments like El Paso County Public Health were recommending that we not test all of our students because the CDC was saying, ‘Don’t test asymptomatic cases.’ Well, that was completely wrong. And so it’s turning out that it’s this big political scandal where reportedly somebody who’s not really a qualified epidemiologist pressured the scientists to change it. And then the website recommendation was changed, without going through the usual process of approval for things to get approval on the CDC website. ... So that’s just really concerning on so many levels because I think the whole world is used to the United States having reliable scientific information that is relatively free from government interference … so, you know, this is a disaster in terms of U.S. relations and kind of for science in general, and I think it’s going to be a long recovery to get the trust back that we had.

CCRP: What are the potential implications of the outbreak at the University of Colorado at Boulder?

Lostroh: Our levels are as high as they were three weeks ago in terms of the number of cases in seven days, and I’m very concerned that we’re back on that exponential increase instead of going down. So that’s been really sad to see, and I think it is connected to Boulder because I think that the whole Front Range — we all drive up and down the front range and go places, and the whole urban part of Colorado is quite connected. So, you know, it’s been about three weeks since Boulder opened and had students on campus; it’s been about three weeks since at least some students who are K–12 started meeting in person here in town. It’s been just a few weeks from Labor Day, maybe not soon enough to feel that Labor Day impact. I think the return to Boulder, which is known for its party culture, is not helping the Front Range at all. ... If you look on The New York Times sites or any of the sites that color the counties to see how serious the cases are, Boulder is the worst and then there’s sort of a gradient going up and down the Front Range. The further you get from Boulder, sort of the better the infection situation is. Maybe if they close the bars earlier, that will help. It’s not going to help house parties, but at least closing the bars earlier or stopping serving alcohol earlier might help. There’s already a mask mandate, so I don’t know if they need to enforce the mask mandate more. Punitive measures pretty much never help in a public health situation, and yet here I am thinking of punitive measures. So then the question is: what positive measures could we do to reach people in the age groups who are gathering at these house parties and/or bars to try to convince them that changing their behavior would be something they would be willing to do because of its consequences for everybody else?

About the CC COVID-19 Reporting Project

The CC COVID-19 Reporting Project is created by Colorado College student journalists Miriam Brown, Arielle Gordon, and Isabel Hicks, in partnership with The Catalyst, Colorado College’s student newspaper. Work by Phoebe Lostroh, Associate Professor of Molecular Biology at CC and National Science Foundation Program Director in Genetic Mechanisms, Molecular and Cellular Biosciences, will appear from time to time, as will infographics by Colorado College students Rana Abdu, Aleesa Chua, Sara Dixon, Jia Mei, and Lindsey Smith.

The project seeks to provide frequent updates about CC and other higher education institutions during the pandemic by providing original reporting, analysis, interviews with campus leaders, and context about what state and national headlines mean for the CC community. 

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