HOUSTON — Houston hospitals have been forced to treat hundreds of COVID-19 patients in their emergency rooms — sometimes for several hours or multiple days — as they scramble to open additional intensive care beds for the wave of seriously ill people streaming through their doors, according to internal numbers shared with NBC News and ProPublica.

At the same time, the region's 12 busiest hospitals are increasingly telling emergency responders that they cannot safely accept new patients, at a rate nearly three times that of a year ago, according to data reviewed by reporters.

The increase in ambulance diversions, coupled with the spike in patients being held indefinitely in emergency rooms, are the latest indicators that Houston hospitals are straining to keep up with a surge of new coronavirus patients. ProPublica and NBC News have previously reported that a public hospital in Houston ran out of a medication to treat COVID-19 patients and that a spike in at-home deaths from cardiac arrest suggests that the death toll from the coronavirus may be higher than official statistics show.

On Thursday, 3,812 people were hospitalized with COVID-19 in the region, including more than 1,000 in intensive care units, a record since the pandemic began. At the same time, since Texas officials have not issued another stay-at-home order to slow the virus's spread, hospitals are also still seeing a steady flow of patients in need of care as a result of car accidents, violent crime and heat-related medical emergencies.

Officials in Houston are warning that the situation could become a replay of what happened in New York City in March and April, when thousands of people died as hospitals struggled to keep up with the surge of patients, but without the same level of government intervention to stem the tide.

Typically when people arrive at a hospital emergency department, they're evaluated and treated by the medical staff. Those sick or injured enough to require hospitalization are then moved to other areas of the hospital for specialized care. But increasingly in Houston, particularly for patients suffering from COVID-19, there's nowhere for them to go.

“Normally that patient would just go to an ICU bed, but because there are no beds available, they continue to board in the emergency room," said Harris Health System president and CEO Esmaeil Porsa, who oversees the city's two public safety-net hospitals. “It is not an optimal level of care. This is not something we would choose to do. The only reason this is happening is because we are being forced to do it."

Although hospital leaders say they are working to provide high-quality care for patients being held in emergency rooms — in part by bringing specialized medical staff and equipment to patients being treated there — studies done before the coronavirus pandemic show that the longer patients stay in ERs, the worse their outcomes.

ICUs and other hospital units are staffed with doctors, nurses and other support personnel who have specialized training and experience caring for critically ill patients in need of specific medical interventions, whereas the mission of emergency department medical workers is to quickly assess patients, stabilize them and get them to where they need to be.

“The problem is you can't get them to where they need to be, and now it puts the ER doc in the position of having to function like the hospitalist or the intensive care doctor, and that's not a role that we're really supposed to be in," said Dr. Cedric Dark, an emergency physician at Baylor College of Medicine in Houston. “The bad thing about having any patient boarded in the emergency department, regardless of the situation, is that it slows down the beginning of care for somebody who needs hospitalization, and the beginning of care for any medical condition is the most crucial period of time."

The same scenario is playing out at hospitals across the Houston region.

A daily status report prepared Wednesday by the SouthEast Texas Regional Advisory Council, which coordinates the Houston region's emergency medical response, showed multiple hospitals running out of immediately available nonsurgical ICU beds, including both of the city's top-tier trauma centers, Ben Taub Hospital and Memorial Hermann's flagship hospital in the Texas Medical Center.

As of Wednesday afternoon, about 145 patients were being held in emergency departments throughout the Memorial Hermann Health System, according to internal numbers provided separately by a Memorial Hermann physician and confirmed by a hospital executive. Several other Houston area hospitals have reported holding multiple patients in their ERs, including four with more than a dozen.

Dr. Jamie McCarthy, an executive vice president at Memorial Hermann Health System and an emergency room physician, acknowledged that the coronavirus crisis has forced his teams to hold more patients in ERs.

“All the hospitals are full," McCarthy said. “All the hospitals in the city are boarding patients. We are expanding capacity, but we can't turn those on immediately. It requires staffing. It requires nurses and doctors to come in. And so, as we've continued to expand our inpatient capacity, we're just keeping up with the volume that's coming in."

It's not unusual for a small number of patients to be held in ERs on busy days, especially during flu season, but three Houston ER physicians said they have never seen so many patients receiving prolonged care in emergency departments, or for such long periods of time.

Although treating patients in the ER for more than a few hours is “not ideal," McCarthy said, Memorial Hermann has worked to mitigate the impact on patients by sending intensive care doctors and other specialists to emergency departments, to ensure patients are receiving quality care regardless of where they're located.

But he warned that there's a limit to what Houston hospitals can do to respond to the crisis.

“We are adding more capacity, but we are absolutely stretched now, and if it keeps going this way, we're going to run out of room. We're going to look like New York," McCarthy said, emphasizing the need for Houston residents to stay home and avoid crowds to slow the virus's spread.

One of Houston's largest hospital systems, HCA Healthcare, also has been caring for dozens of COVID-19 patients in its emergency departments. In a statement, HCA spokeswoman Debra Burbridge said hospital officials have taken steps to reduce the impact on patients, including sending staff members who would normally be performing or assisting with elective surgeries — which have been suspended under an order by the governor — to treat patients with COVID-19.

Dr. Kusum Mathews, an assistant professor of critical care and emergency medicine at the Icahn School of Medicine at Mount Sinai in New York, said hospitals can take steps to reduce the risks of overcrowded ERs, including some of those described by Memorial Hermann and HCA officials.

Treating patients sickened by the virus “has outstripped every stretch of our imagination," Mathews said. “We have had to put beds in hallways, double up patient rooms … just to allow for offloading the emergency department to get more patients in."

While Houston's top hospital executives have repeatedly said they can add hundreds of new intensive care beds to meet the demand, at least for the next couple of weeks, the number of patients being treated in emergency rooms demonstrates the difficulty of executing those plans in the midst of a rapidly growing crisis, officials say.

“Those things are not like a switch-key type of activity," said Porsa, the Harris Health System CEO, noting that his hospitals have had to send patients to hospitals outside of Houston to make room. “The bottleneck to do that is really staffing. As you can imagine, ICU nurses are not a dime a dozen. They are very hard to come by, and it takes time to actually be able to do that."

The logjam of patients being treated in ERs has also led to delayed emergency response times across the city, according to Houston Fire Department officials.

When hospitals get overloaded, they ask regional authorities to divert ambulances elsewhere. For example, Memorial Hermann's northeast hospital was on diversion status just 2% of the time during an eight-day period in late June and early July last year; it was on diversion status 58% of the time during the same time period this year. At Houston's busiest public hospital, Ben Taub, the number jumped to 81% from 58%.

The problem, said Houston Fire Department Assistant Chief Matt White, is that when every hospital is maxed out, ambulance crews have no choice but to take patients to emergency departments that are too busy to quickly receive them. And by law, hospitals must screen and stabilize any patient who arrives.

“When everyone is on diversion," White said, “nobody is on diversion."

Earlier coronavirus outbreaks inundated emergency rooms in New York City and Detroit, but lockdown orders in those cities led to fewer car accidents and a reduction in violent crime, freeing more space in ERs for COVID patients.

With most Texas businesses still open and no mandatory stay-at-home order, hospitals in Houston and other COVID-19 hot spots face the added challenge of making room for COVID patients while still dealing with a steady flow of patients seeking care for other medical emergencies.

And across the country, people with chronic health problems who delayed seeking care earlier in the pandemic are now showing up for treatment, taking up beds, said Dr. Marc Eckstein, medical director of the Los Angeles Fire Department and a professor of emergency medicine at Keck School of Medicine of the University of Southern California.

Despite these challenges, McCarthy, the Memorial Hermann executive, said it's essential that people continue to come to the hospital for medical emergencies. He pointed to an NBC News and ProPublicareport this week that showed a growing number of people are dying suddenly at home, before emergency responders can reach them.

“If a patient believes they have a serious medical issue, they still need to come to the emergency department," McCarthy said. “We will make the capacity to take care of them. Delaying care for time-sensitive emergencies is time we don't get back. If they wait to call for help when they are having a heart attack, it will be worse than if they come in early."