LAREDO, Tex. — Leaders in this border city have implemented some of the strictest coronavirus control measures of any in America — with curfews, anti-gathering orders and a requirement to wear masks — seeing themselves as the first line of defense in protecting the nation's most important commercial corridor.

With four bridges and a rail line bringing goods into the country from Mexico, Laredo is the fulcrum of a delicate supply chain that generates billions of dollars in trade and brings crucial supplies, including produce and medical and electrical equipment, into the country.

From here, via Interstate 35, most everything that crosses the border goes north to San Antonio, and then to points across the country, stocking shelves from California to New York and everywhere in between. City officials worry that viral spread in Laredo could mean a threat to the entire nation, as products, trucks and their drivers disperse along the highways.

Eleven virus-related deaths here in the past 19 days — including a one-week span with six deaths — have pushed Laredo and its surrounding county to the highest death toll of any Texas border community. It has the city of approximately 260,000 worried that the disease could consume limited resources and perhaps lead to a devastating shutdown of operations. The lack of testing — less than 1 percent of residents have been tested thus far — and fears of a slow response to the virus in densely populated Mexico create additional concerns.

Most of the more than 200 positive cases in Laredo were transmitted locally, said Hector Gonzalez, the director of the city’s health department. He said it is critical for Laredo to get its outbreak under control because of the outsize effect that spread here could have on the country.

“We were proactive in doing things that were not being done yet in most of the country because we are trying to prevent this thing from getting out of control and taking more lives,” said Victor Trevino, the Laredo Health Department’s health authority. “We have very few weapons and are making do with what we have to protect our city and the country’s No. 1 land port. We are balancing our health with the business of the country.”

While some parts of rural middle America have not yet instituted stay-at-home orders or social distancing, Laredo’s City Council acted as it saw its first cases in late March, implementing curfews and threatening residents with fines of up to $1,000 if they didn’t cover their faces with masks when out in public. Police have been breaking up backyard parties and monitoring homes where too many cars are parked.

Truck drivers are no longer permitted to get out of their cabs at U.S. Customs and Border Protection checkpoints, and they drop their cargo in Laredo warehouses without touching the merchandise. Warehouse workers are wearing protective equipment, and companies are staggering shifts to keep a small number of people working at any time.

Mayor Pete Saenz Jr. (D) said he sees it all as preventive management.

“No one knows where this thing is going to take us,” Saenz said. “The only tool we have is isolation. Once it surpasses us, we’ve lost the battle.”

To follow the local mask ordinance, Laredo residents can use any cloth covering, including bandannas or scarves, to cover their nose and mouth if they are going to a grocery store or getting outdoor exercise. Community groups are working to sew homemade masks by the hundreds.

Police have issued nearly two dozen citations for those not wearing masks, and they have received complaints that have resulted in warnings, Laredo Police Chief Claudio Treviño said. Off-duty officers have embedded inside businesses to help spot violators, with 70 working as a special team patrolling the streets.

“Now it feels weird to see someone who isn’t wearing a mask,” said Lucy DeLeon, co-pastor of New Vision Community Church. “People are really afraid and doing their part.”

Roberto “Bobby” Quintana’s aunt and mother died within a day of each other — on March 21 and March 22 — the first two deaths recorded in Webb County. His father and brother are on ventilators. His sister tested positive but is at home; his cousin recovered after hospitalization.

Quintana, a Webb County justice of the peace, said he has no idea how the virus reached his family, but many relatives work in law enforcement and at the county jail and could have carried it to frequent weekend gatherings. The last time he saw his mother was at her house the Saturday before she was intubated at the hospital. Quintana has not yet been able to bury her, and he hasn’t been able to tell his father that she is dead.

“I think about it but I don’t want to blame anyone. It really doesn’t matter where it came from, the thing is, they got infected,” he said. “Every single day my phone rings and I’m afraid to pick it up because I don’t want to get that call again.”

The ruthless efficiency of the virus makes Quintana’s border town uniquely susceptible, he said. The local economy depends on the uninterrupted movement of hundreds of thousands of people and massive amounts of goods that can become carriers of the contagion. The U.S.-Mexico border is the busiest in the world, and trade in Laredo comprises half of all commerce along Texas’s 11 land ports.

Doctors at Laredo’s two main hospitals said nearly 60 health-care workers have fallen ill, with numerous doctors and nurses, including the city’s critical care pulmonologist, having come in contact with asymptomatic patients who had been exposed to the virus.

Physicians said dozens of patients a day enter the city’s emergency rooms after having been sent home by their family doctors, complaining of losing their sense of taste and other mild symptoms associated with the coronavirus.

“I am convinced that we have well over 2,000 positives in Laredo,” said Ricardo Cigarroa, a doctor who makes 40 to 50 house calls a day for patients he believes have the virus but do not appear in official counts because they have not been tested. “It’s impossible to predict, but from a front-line physician’s perspective, I have great fear.”

That kind of anxiety fueled early rumors of a potential border shutdown. U.S. Customs and Border Protection (CBP) has worked to keep the crossing open to avoid crushing the economies of Laredo and its sister city in Mexico, Nuevo Laredo. Federal authorities instead have restricted border crossings to essential travelers, which includes U.S. citizens and anyone going to school, for medical treatment, or to work in Texas.

CBP officials said agents are following guidelines from the Centers for Disease Control and Prevention and have been providing employees with gloves and masks; seven CBP Laredo agents and officers have tested positive.

Anyone who appears sick at the ports is turned back to Mexico, said Rick Pauza, a spokesman for the CBP in Laredo. He did not say how many people, cars or trucks the agency has turned back since the restrictions went into effect March 20.

U.S. authorities have been aggressively turning away migrants at the border during the pandemic, using emergency health orders to effectively shut down the asylum system and immediately eject undocumented people from the country, on average in just more than 90 minutes.

So far, truck traffic from Mexico has declined by about 7 percent. But pedestrian traffic has plummeted approximately 50 percent, and U.S. Rep. Henry Cuellar (D), who represents the district that includes his hometown of Laredo, said he wonders if there isn’t more that can be done to screen travelers. The drop in travelers is reassuring for Laredo’s health but it also means significant revenue loss from the bridge fees the city collects.

“The numbers have dropped considerably, but people are still coming,” Cuellar said. “If something goes wrong, that affects everything else.”

Across the border in Nuevo Laredo, customs officers are taking more aggressive steps to slow down foot traffic into Mexico. They are asking travelers from the United States to justify their trips in detail and are using forehead thermometers to screen for coronavirus symptoms.

“If you don’t have a reason to cross, you don’t cross,” said Elia Guevara, a licensed customs broker in Nuevo Laredo.

The health crisis has shut down U.S. auto manufacturing plants in Mexico, shifting demand toward medical supplies and food. Everything from toilet paper to brand-name household disinfectants such as Clorox are being loaded onto about 14,000 trucks a day crossing Laredo’s ports of entry, customs broker Arturo Dominguez said.

“If we were to collapse, shipments would be delayed tremendously, and whatever the country needs won’t arrive,” Dominguez said. “The rest of the country depends on the health of our port.”

Ernesto Gaytan Jr., president of the Laredo Motor Carriers Association, said none of his truckers have fallen ill, but he is bracing for the worst-case scenario. One of his drivers was worried this week because he was transporting a load of transformers to a hospital in New York, where the worst outbreak in the country is ongoing. Gaytan had to reassure him.

“This is potentially lifesaving work we are doing here,” Gaytan said. “Giving energy to a hospital that needs the equipment.”

City leaders worry that without more help from the state and federal governments, it could miss an opportunity to arrest the spread of the virus because of its lack of testing capabilities. Texas broadly lags behind the rest of the nation in testing. The city has been able to test less than 1 percent of its residents and had to scrap a supply of rapid-test kits it obtained from a Chinese manufacturer because they did not work.

Gonzalez, the city health director, said he hopes the state’s supply of coronavirus test kits from Abbott Laboratories will help Laredo ramp up testing, but it will take time. Some civic and business leaders say they worry that the city has not received much attention during the crisis, and that could lead to people underestimating what an outbreak here could mean for the rest of the country.

“Being on the frontera means we are far away from Washington and Austin,” Laredo City Councilman George Altgelt said. “We realize that this a self-rescue mission and that the federal government is not coming to save us. Trade is our lifeblood and the nation’s, and we are willing to do our part. But will they do theirs?”