10.7% of Texans have contracted COVID-19, UT model estimates

Texas

Austin (KXAN) — A new report by the COVID-19 pandemic modeling team at UT Austin estimates 10.7% of all Texans have contracted COVID-19 since the pandemic began. This report was published Wednesday and shared with the Texas Department of State Health Services.

The report analyzed COVID-19 hospitalizations between April 11 and August 11, as well as demographic data, and anonymized cell phone movement data from the 22 Trauma Service Areas (TSA’s) in Texas .

The UT researchers’ projections indicate that the recent surge of COVID-19 transmission across Texas is now declining across most regions, as is the threat that hospital and ICU capacity will be exceeded in the upcoming weeks. However, Dr. Lauren Ancel Meyers, a UT professor of integrative biology, who wrote this report said these projections should not be interpreted to mean that Texans can let their guard down when it comes to protecting against COVID-19.

“It means the exact opposite, it means that the precautionary measures that we have put in place over the last month or so have really had the desired effect, that by wearing masks, by keeping our distance, by limiting our activities outside of our houses, [limiting] the number of people we interact with, we’ve actually been able to slow transmission at a point in time where things were really jeopardizing the safety and integrity of our health care systems,” Meyers said.

“If we do not continue to do that, we will repeat history and we will see the virus start spreading again,” she continued, noting that relaxing on these precautionary measures could result in further strain on local healthcare systems.

“What I’m saying is that there’s a reason that we’ve seen a decline across Texas [in COVID-19 transmission] and that’s because our behavior changed, our policies changed and we’ve been doing things on a concerted basis to slow the spread of the virus,” she emphasized.

It is possible, Meyers said, that if Texans become more relaxed about precautionary measures that another wave of the virus could occur.

Meyers works on UT’s COVID-19 Modeling Consortium, a team of researchers with pandemic modeling expertise that long precedes the coronavirus pandemic. The consortium has focused on modeling COVID-19 spread over the past few months with the aim of providing information to help policymakers come to more informed decisions. Reports they have produced about COVID-19 have been shared with local, state, and federal leaders.

The researchers note that these models are based on certain assumptions (such as how age impacts the spread of the virus and how the virus is transmitted between asymptomatic people). They explained that these projections don’t show the full range of uncertainty, but rather, aim to offer basic insight into the changes in risk of transmission and healthcare surges across Texas.

As with many of their other COVID-19 modeling reports, these results are being posted prior to peer review so the information can be used by the public and policymakers to make decisions about the immediate threat of COVID-19. This is work the researchers expect to continue to update as more hospitalization data becomes available

Transmission of COVID-19

The estimates in this report indicate every single one of the 22 TSA regions in Texas saw a surge in COVID-19 cases, hospitalizations and deaths, with transmission starting to rise in early May. Transmission rates in these areas have declined since the researchers published a previous report on July 22, with only two regions having more than a 50% chance of a growing epidemic: Amarillo and Belton/ Killeen.

According to the report, eight regions have a probability of more than 90% that the epidemic is declining: Lubbock Abilene, Dallas/ Fort Worth, El Paso, San Angelo, Austin, Corpus Christi, and the Lower Rio Grande Valley.

COVID-19 prevalence and incident rates for each of the 22 Texas TSA regions as listed in UT’s COVID-19 Modeling Consortium report on August 19, 2020.

“While COVID-19 is still straining healthcare systems across the state, the risks of overwhelming surges have diminished,” the report said.

While the report shows there is a 99% chance probability that the pandemic is declining statewide, Meyers points out that the probability varies considerably in different regions (Amarillo, for example, has only a 24.6% probability that the epidemic is declining).

This report looked at “reproduction number” which indicates the contagiousness of the virus at any given time. If a reproduction rate is greater than one, the epidemic will continue to grow and if the reproduction is less than one the epidemic will begin to subside, the researchers explained.

The researchers noted that behaviors like wearing masks and social distancing can help reduce how fast the virus reproduces.

In many of these Texas regions, the reproduction number of COVID-19 increased after the relaxation of March- April stay home orders, the researchers said. For most of these regions, the report estimated that COVID-19 transmission peaked in mid-June and then declined into early August with most regions seeing declining risk in recent weeks.

While the researchers estimate that 10.7% of Texans have contracted the virus over the entire course of the pandemic, they also estimated that on the day of August 11 alone, 0.3% of Texans had COVID-19.

The researchers also estimate the Texas regions that have had the largest percentages of people who’ve contracted the virus over the course of the pandemic are: Victoria (15%), Dallas/ Fort Worth (14.7%), and the Lower Rio Grande Valley (12.1%).

Austin is estimated to have a 94.6% chance the pandemic is declining. The researchers also estimate that 5.4% of the Austin population has contracted COVID-19 throughout the entire course of the pandemic.

COVID-19 reproduction rates for each of the 22 Texas TSA regions as listed in UT’s COVID-19 Modeling Consortium report on August 19, 2020.

Hospital capacity

In all of the 22 areas shown in the report, the risk of exceeding general hospital capacity in the next three weeks is below 10%, the researchers found, with the highest risks estimated for Laredo (10%) and Belton/ Killeen (9.4%).

The researchers used “spaghetti line” graphs to illustrate their projections for the range of uncertainty, with each line representing an equally likely future path. The bold line on these graphs shows the median across the different trends.

COVID-19 hospitalization projections through September 1 for each of the 22 Texas TSA regions as listed in UT’s COVID-19 Modeling Consortium report on August 19, 2020.

ICU capacity

The researchers said their projections suggest COVID-19 cases are likely to exceed an area’s ICU capacity before they exceed general hospital capacity.

Only six areas have more than 10% risk of exceeding non-surge ICU bed capacity: Amarillo 48%, Belton/ Killeen 35%, Laredo 19.8%  San Angelo 18% Wichita Falls 12.2% and Galveston 10.8%

Probability of exceeding hospital and ICU capacity for each of the 22 Texas TSA regions as listed in UT’s COVID-19 Modeling Consortium report on August 19, 2020.

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