The coronavirus outbreak in Mexico’s steel capital started at the very place that was supposed to help stop it.

Social Security Hospital No. 7, a towering 240-bed facility, is the main public medical center in the northern city of Monclova. But when a 42-year-old truck driver arrived with pneumonia-like symptoms last month, the hospital didn’t isolate him. Within two weeks, he was dead of covid-19.

Soon, a doctor and an administrator had also perished. Ultimately, 41 employees of the hospital wound up testing positive for the virus.

It was the first in a series of outbreaks at hospitals that have rattled Mexicans and raised questions about the Social Security Institute, the country’s biggest public health network. Nurses and doctors have held protests around the country. The governor of Baja California, Jaime Bonilla, lashed out at federal authorities for the lack of protective gear in his border state, saying doctors were “dropping like flies.”

Medical personnel in other pandemic hot spots, such as Italy and Spain, have also expressed outrage about working without proper equipment. But Mexico is particularly vulnerable, because it has many fewer doctors and nurses per capita.

“The European systems are better financed per capita, and much bigger as a percentage of GDP,” said Eduardo González-Pier, a former deputy health minister. Mexico’s public health system has been underfinanced in recent years, he said, leaving it “more fragile, less well-equipped.”

At least 686 people in Mexico have died of covid-19, according to authorities. About 9 percent of the country’s confirmed cases — 535 people — are employees of the Social Security Institute, known by its Spanish acronym IMSS. They make up around half the Mexican medical professionals who have been infected, officials say.

Unlike in the United States, most people in Mexico receive health care through the government. And no provider is more important than the IMSS, which serves about half the population. It operates more than 350 hospitals and thousands of clinics, the largest public health network in Latin America.

The Monclova hospital, less than three hours from Eagle Pass, Tex., is one of those hospitals.

The truck driver, who was admitted in mid-March, was sent to a bed in the emergency department. He remained there for days until it was confirmed that he had covid-19, said Roberto Bernal, the health secretary for Coahuila state. Few coronavirus tests were available in Mexico at the time.

“It’s three shifts of people, morning, evening and night” in the emergency room, Bernal said. “Imagine what a petri dish of contamination it was.”

Even before the driver died, doctors and nurses at the hospital began holding demonstrations to protest their lack of protective gear.

“There’s no material, no equipment — gloves, masks, there’s never any of that,” nurse Arturo Ramírez told the Televisa network.

Nearly half of the 230 confirmed cases in Coahuila state are medical personnel, according to the governor. The head of Hospital No. 7 had been replaced.

The Monclova outbreak was followed by flare-ups in other hospitals. In the resort city of Cabo San Lucas, two employees at Hospital No. 26 developed symptoms, so authorities tested the entire staff. Forty-two had the virus.

In Tlalnepantla, outside Mexico City, 44 personnel at Hospital No. 72 turned out to be positive, according to IMSS. They included a group of medical residents who had been pressing their supervisors to give them protective equipment. The young physicians were told that buying their own gear was part of their “commitment” to medicine, they wrote in a letter published in Mexican media.

A senior IMSS official, Víctor Borja, said some of the hospital outbreaks were unsurprising, given that they were in areas with high levels of contagion. And in several cases, he said, medical personnel contracted the coronavirus outside the hospital — on trips or at social gatherings.

But he acknowledged that staff were initially underequipped for the pandemic. Authorities started ordering extra protective gear in late February, he said.

“At the beginning, we had a problem because there were shortages both nationally and internationally,” said Borja, the head of medical benefits at the IMSS. “Every country was competing” to buy the same items.

Another problem, he said: The initial definition used by medical authorities to determine what constituted a coronavirus case was too restrictive. They focused on people they knew had traveled abroad or had contact with carriers, rather than everyone who showed possible symptoms. The truck driver didn’t initially say that he had recently been to the United States, Borja said, slowing the diagnosis.

“The important thing is what we’ve learned from these outbreaks,” Borja said, such as the need to disinfect facilities rapidly. Mexican authorities have received tons of imported medical equipment in recent days, which should resolve the shortages, he said. They have also announced 20 percent bonuses for IMSS employees who treat covid-19 patients.

The challenges in the Mexican public health system go well beyond the coronavirus.

The IMSS, founded in 1943, was a pioneer among Latin American social welfare institutions. Its surgeons performed Mexico’s first kidney transplant in 1963 and its first heart transplant in 1988.

But in recent years, the institute’s finances have taken a hit as the population has aged, requiring more expensive health care, and pension costs for medical personnel have risen.

“The IMSS has had slender financial margins for years,” González-Pier said. “You can see this reflected in low investment in hospitals and equipment.”

New policies introduced by President Andrés Manuel López Obrador after taking office in December 2018 have further complicated matters.

López Obrador centralized government purchasing of medicines to cut costs and discourage corruption. But that resulted in shortages of drugs. He launched an austerity campaign that so angered IMSS head Germán Martínez that he quit last May. Martínez called the cuts in health spending “inhumane.”

López Obrador also overhauled Insabi, another major public health system, aimed at the poorest Mexicans. (IMSS is largely for salary-earners.) But its rollout has been bumpy.

The recent shortcomings at the IMSS hospitals have raised so much concern that state governments and business groups have been donating masks and other equipment to the facilities.

Eugenio Derbez, a well-known actor here, appealed on Twitter for followers to provide protective gear to IMSS Hospital No. 20 in Tijuana. He had received a letter from a doctor saying the facility was “overwhelmed.” His video, posted last Sunday, went viral.

IMSS responded that the hospital had adequate equipment. But Bonilla, the Baja California governor, backed the actor, saying medical personnel were poorly outfitted.

“They are dropping like flies,” said Bonilla, who belongs to López Obrador’s Morena party.

Borja said 24 staff at the Tijuana hospital have tested positive for the coronavirus. He said the virus was apparently introduced by a nurse who might have been infected outside the facility.

He acknowledged that IMSS has lacked sufficient infrastructure for some time. It had drawn up plans to expand the number of beds for its clients. Then came the coronavirus.

“You can’t build a hospital overnight,” he said.

Gabriela Martínez contributed to this report.