UTSA professor behind COVID-19 model says early response ‘prevented explosion in cases’ in Bexar County

Dr. Juan Gutierrez said inaction would have resulted in thousands of cases

SAN ANTONIO – When Dr. Juan Gutierrez, the chair of mathematics at UTSA, was tabbed to create one of the four COVID-19 models for the City of San Antonio and Bexar County, he knew the challenge that lied ahead for his team.

Gutierrez had been studying the pathogen’s progress globally. His first report was released April 15 on the city’s website and showed that with current social distancing restrictions in place, we were expected to reach 3,600 total cases by August.

But more startling to Gutierrez was what would have happened had social distancing restrictions, such as the “Stay Home, Work Safe,” orders not been in place in Bexar County.

“An early response prevented an explosion in the number of cases. Had the Mayor (Nirenberg) and County Judge (Wolff) not acted early, the crisis would have been significantly larger,” Gutierrez wrote in his initial report. “The city lockdown has slowed down the progression of the disease. It allowed the health system to prepare for what is likely to be an inevitable surge.”

RELATED: COVID-19 projections show different outcomes in San Antonio, Bexar County

Gutierrez ran the simulations if we returned to normal and saw catastrophic results. His initial report noted that the Bexar County area would reach 920,000 total cases with a peak of 380,000 active cases.

“I ran the simulations of what would have happened had the restrictions delayed one single week and the number was thousands more cases,” Gutierrez said in an interview with KSAT 12.

Gutierrez researched malaria for over a decade and created multi-scale models to track that particular infectious disease. That helped him recognize the challenge in tracking COVID-19.

“Once authorities started locking down towns, then regions, they were always one week behind the disease,” said Gutierrez.

Gutierrez studied asymptomatic carriers, meaning individuals that carry and spread the disease despite showing no symptoms, and saw disturbing trends with COVID-19.

“Once this started spreading like wildfire with dry bushes, it was painfully evident to me and to others who work in the field that these could only be driven by asymptomatic carriers,” Gutierrez said. “This was spreading at an unprecedented speed.”

The models have changed since his first report in mid-April, but that was to be expected. Gutierrez compared creating models for the virus to tracking a hurricane.

“When you see a model, just pay attention to the date,” Gutierrez said. “Like hurricanes, those projections change every single day before the storm hits the ground.”

Gutierrez said more test results have helped shape current models, but we will always naturally be behind the pathogen. That is in part because identifying people who have been infected takes place when there is already community transmission.

“All of this gives us an imperfect view of reality in the task of modeling and quantifying the possible scenarios,” Gutierrez said.

“Metro Health in San Antonio has been doing a good job given the constraints that we have,” Gutierrez said. “Essentially the main constraint is the lack of testing. These tests take time.”

Gutierrez’s models change by the day. His latest report estimated anywhere from 1,800 to 3,800 active cases through Aug. 27. However, the peak may have shifted as well.

“Given the fact that there is delay in reporting a time lag between the moment of sample collection and the moment that that is reported by Metro Health, it is quite possible that we have already peaked under current conditions in San Antonio,” said Gutierrez.

Gutierrez is confident we are ahead of the curve and said San Antonio is moving in a very good trajectory, but the key to studying COVID-19 remains in the unknown, how many asymptomatic carriers are spreading the virus.

“This phenomenon of asymptomaticity is very common in many diseases and in many epidemic events, asymptomatic carriers are the one driving the epidemic,” said Gutierrez. “This is a very contagious pathogen. We have never seen a pathogen like that.”

COVID-19, the respiratory disease caused by the new virus, stands for coronavirus disease 2019. The disease first appeared in late 2019 in Wuhan, China, but spread around the world in early 2020, causing the World Health Organization to declare a pandemic in March.


About the Authors

RJ Marquez is the traffic anchor/reporter for KSAT’s Good Morning San Antonio. He also fills in as a news anchor and has covered stories from breaking news and Fiesta to Spurs championships and high school sports. RJ started at KSAT in 2010. He is proud to serve our viewers and be a part of the culture and community that makes San Antonio great.

Valerie Gomez is lead video editor and graphic artist for KSAT Explains. She began her career in 2014 and has been with KSAT since 2017. She helped create KSAT’s first digital-only newscast in 2018, and her work on KSAT Explains and various specials have earned her a Gracie Award from the Alliance for Women in Media and multiple Emmy nominations.

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