Local health officials made a startling discovery when they tested people in packed coronavirus hot spots.

Most of those who were positive had no symptoms at all.

On Wednesday, no fewer than 222 of 259 inmates at Bexar County Jail who were positive and presumably contagious did not feel sick. At the Southeast Nursing and Rehabilitation Center, where at least 18 residents have been killed by the virus, 56 of 74 residents who tested positive showed no signs of illness.

The tests indicate the dangerous and sometimes deadly virus is even more infectious than previously understood, potentially spreading rapidly on the streets from symptom-free carriers as Texas slowly reopens its smothered economy.

The ongoing risk poses profound public health implications as people begin to venture from their homes to resume their lives and reclaim their livelihoods.

To hold the epidemic at bay, experts say social distancing must be maintained.

In some ways, the jail is very much a mirror of the rest of the community, so what were seeing there is very much reflected in our community here in San Antonio, said Dr. Bryan Alsip, University Health Systems chief medical officer and a member of the city and countys health transition team.

Nationally, the data around asymptomatic COVID infections range anywhere from 20 to more than 60 percent, Alsip continued. And so what weve seen in the jail, weve seen asymptomatic positives at a percentage as high as 70 percent. If we were to test all of our individuals here in San Antonio, we may see similar percentages. We just dont know yet.

To better understand the spread, Metro Health has launched widespread testing at six other nursing homes with positive cases and Thursday opened two sites where for the first time those with no symptoms could get tested. Soon, the department will conduct a study of randomly selected households to determine just how pervasive the virus could be.

Dr. Juan Gutierrez, chairman of UTSAs math department, has a strong suspicion.

As Gutierrez watched the coronavirus blanket the globe earlier this year, he suspected that symptom-free carriers of the virus were driving its exponential spread.

Last month, Gutierrez produced a model of the local epidemic that relied on his understanding of the diseases R0 pronounced R-naught meaning the average number of new infections thought to arise from a single case. The variable, known as the basic reproduction number, can fluctuate from place to place and over time as human behavior changes.

Gutierrezs model accurately projected a peak here in early May. He estimated the R0 of the virus at about 13, much higher than generally believed. Now, as health officials realize that symptom-free carriers of the virus are more abundant than previously thought, Gutierrez believes his analysis has been justified.

My group was the first group to report that R0 was extremely high for COVID-19, Gutierrez said. It was received with disbelief. And it was received with disbelief because there was a poor understanding of the role of asymptomatic carriers. Now, as time passes, the months pass and more evidence is accumulated, I have been proven right. I was right when I said R0 is very high.

He pointed to a recent analysis of data in China that suggested about four in five coronavirus infections cause no symptoms.

Eighty percent is what seems to be the level that evidence suggests, said Gutierrez, who has spent a decade researching symptom-free carriers of infectious disease.

At this level, we have tremendous challenges controlling the disease, he continued. The progression of the disease is accelerated by the number of asymptomatic people. There are many people in the community who dont know theyre sick and are passing it to others. Thats probably where we are, and that is the only possible explanation for the very fast spread of this disease.

Bexar County is an outlier among major cities in Texas because it has managed to keep infection rates low, Gutierrez said. As the state begins to reopen, its critical for residents to maintain strong hygiene and social distancing measures wear a mask in public, stay 6 feet away from others and constantly wash your hands, he said.

I think that we might have a chance to keep this disease at a low level, Gutierrez said.

The uncertainty is what drove Leticia Garcia to get tested Thursday.

Garcia was feeling just fine. The 53-year-old cancer survivor lined up anyway with about 50 others in the parking lot of the Las Palmas Branch Library to receive a free test the first time anyone in Bexar County could get tested for the virus regardless of whether they had any symptoms.

The walk-up testing is available from 10 a.m. to 2 p.m. today and Saturday at the library branch and Woodlawn Lake Park, with results available within 48 hours. Garcia was there in part because shed heard how many inmates at the jail had tested positive despite showing no symptoms.

So you dont know if youre carrying (the virus) and youre walking around, Garcia said. You can never tell who has it. So many people have tested positive and theyre asymptomatic. Why are we opening up the city, the state?

Metro Health Director Dawn Emerick said last week that the county would continue to limit tests in the general population to those with symptoms at least until a study is completed showing how many residents with no symptoms are infected and unwittingly spreading the virus.

In the next few weeks, researchers will pick 385 households at random and test them for the virus.

Until we know what the positivity rate is of asymptomatics, all were doing is throwing strategy on the wall to see what sticks, Emerick said then. And I think thats bad practice. Theres no local evidence right now that is indicating we should be redirecting our resources in that manner. Our focus should be on those with symptoms and high-risk, congregant settings.

But new guidance from the Centers for Disease Control and Prevention this week prompted the revised rules at the walk-up sites, said Jennifer Herriott, assistant director at Metro Health.

Just within the last 24 hours, the CDC revised their guidelines in terms of who should get tested, Herriott said Thursday at the Las Palmas site. They identified specifically that communities of color and high risk areas should be included regardless of their symptoms. The South Side, the West Side and the East Side of San Antonio have large pockets in which we have both communities of color and a lot of poverty.

Teresa Gonzalez, 65, arrived early for the free nasal swab test.

I have a scratchy throat and a cough, she said. I think its allergies. I dont know.

Her 68-year-old husband, Joel, felt fine. But he regularly cares for his mother and father, who are 93 and 94, he said, and he doesnt want to infect them unwittingly.

The older they are, the more vulnerable to get sick, Joel said.

Nearby, a woman with a cane who only would give her name as Adriana M. also had come for a test because she regularly cares for her elderly parents.

Hey, thats what us Mexicans do, said Adriana, 53, who said she suffers from diabetes, asthma and high-blood pressure. Our parents showed us. We follow the chain of command. So now my boys are doing that with me.

Metro Health will track those with no symptoms who test positive at the new sites, Herriott said.

I will absolutely be including that as a question, she said, because I think its going to be very important for us to determine whether people who were asymptomatic when they came to get tested today are actually positive.

Bexar County Judge Nelson Wolff suggested this week at a news briefing that the number could be quite high.

I believe that what were seeing here is that you and I or anybody in this room couldve had COVID, Wolff said. We didnt know we had it. We never got sick. But its out there, and I think the jail is an indication that a pretty good percent of people out there do have it.

He added, Thats why we keep saying over and over again, I dont care if you think youre healthy or not, wear the mask, stay 6 feet away, wash your hands, sanitize.

bchasnoff@express-news.net

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Experts: Even without symptoms, many can spread the coronavirus - San Antonio Express-News