CHICAGO — As this city braces for April 20, the anticipated peak of coronavirus infections here, doctors and nurses at Rush University Medical Center say they are prepared, not just because of their training, but because of where they work: A 14-story, 830,000-square-foot facility built specifically for a deadly pandemic.

The butterfly-shaped building, known as “the Tower,” opened in January 2012 as the first of its kind in the United States. Built at a cost of $654 million in the shadow of 9/11 and the anthrax attacks, the facility was designed to be able to quickly handle waves of patients, expand its bed capacity to 133 percent and control airflow to entire sections of the structure to prevent cross-contamination.

The coronavirus is the first major test of the facility’s strengths and also its agility in the face of a rapidly increasing death toll in Illinois. As of Thursday afternoon, there were 16,422 cases in Illinois, 528 of which resulted in death. Rush has approximately 20 percent of the ventilated cases in the entire state.

“In the wake of 9/11, they began to rethink this idea of how to deal with mass casualties,” said Jerry Johnson of Perkins & Will, the principal architect behind the medical center. “Other hospitals tried to address some of these issues, but it was the first to deal with all of these issues at once with one facility. They were really visionary.”

The first coronavirus patient showed up at Rush on March 4. Eleven days later, the hospital switched to “surge mode” for the first time in its history to accommodate what could be a flood of patients based on modeling.

At Rush, that means an ambulance bay was refashioned into a triage area where up to 100 patients with covid-19, the disease caused by the coronavirus, can be screened each day. Patients sit in chairs spaced 6 feet apart on the concrete floor and wait to be examined in one of two blue tents designed to isolate them from others in the ambulance bay.

“By setting up there, it allows for patients to be kept out of the remaining emergency hospital where they could infect other people. That makes a big difference” in isolating the spread, said Marvina Williams, a senior medical planner at Perkins & Will who led planning for the emergency room.

The bay is also a mass decontamination area where patients and even ambulances can be washed if needed. Under the floor are 10,000-gallon holding tanks to prevent the water used to clean contaminated patients from entering the city’s wastewater system.

Patients with severe covid-19 symptoms are escorted to the emergency room. Those in less severe condition are sent home with a strict 14-day quarantine order.

The permanent emergency room at Rush is unlike most: Instead of curtains, each bed unit has its own set of thick glass doors to seal it off, with a negative-pressure air system to prevent infection from escaping into common areas. Before sliding the doors open, nurses suit up: a yellow smock, a mask, gloves and a pair of goggles. The ER has 60 beds, but during a surge each unit can be doubled to increase capacity to 120 beds.

“We have not doubled up yet, but that is our apocalypse plan, knock on wood,” said Yanina Purim-Shem-Tov, medical director of the Rush Outpatient Chest Pain Center who operates out of the Department of Emergency Medicine.

Under the surge, routine ER patients — someone with a broken ankle, for example — are handled in the building’s main atrium, which has been outfitted as “a MASH unit,” completely cut off from the covid-19 patients in the emergency section, said Purim-Shem-Tov. The atrium’s design made the transformation easy: Disguised inside every support column are panels giving access to oxygen and other necessary medical gases, as well as electricity. Non-emergency physicians, such as pediatricians, are staffing the MASH unit.

Using the atrium as an extra medical bay is an idea that originated at Rush, said Williams. The scene is quite different at older hospitals in coronavirus hot spots around the country, such as New York City.

“Nowadays you are seeing overloaded hallways and you have to bring in oxygen by portable tanks,” Williams said. “Having the foresight to do something like that really made a difference.”

Located along the Interstate 290 expressway and just west of Chicago’s downtown lakefront, Rush is an academic health system that includes the main medical center, plus four other locations in the city and nearby suburbs. Funding for the Tower came from private grants, contributions and federal agencies, including the Energy Department and the Defense Department.

On a recent morning, the atrium is empty. Non-coronavirus patients are staying home, despite their injuries, afraid they’ll become infected at the hospital, Purim-Shem-Tov said. A typical Monday at Rush might bring 240 people to the emergency room. Now that number is about 155, she said.

But the ER is sending an increasing number of patients to intensive care. Typically, 2 percent of ER patients are transferred to the intensive care unit. Last week, that rose to 10 percent, Purim-Shem-Tov said. The most patients admitted to the ICU in a single day so far has been 21, said ICU Medical Director Mark Yoder.

Capacity in the ICU is becoming a challenge as patients are not recovering quickly and are staying longer. Rush has already filled its ICU floor, plus another floor outfitted for ICU patients. On Saturday, it started sending ICU patients to a third floor. The Tower’s total critical-care bed capacity on the top five floors is 304.

The volume has stressed nurses who have had to forgo frequently turning patients, checking blood sugar levels and examining chart notes, Yoder said. They “can’t operate at [the] high level” they are used to, he said. Monitors and supplies are kept in the hallways so nurses don’t have to go in and out of the rooms as frequently. “Precautions” needed to interact with coronavirus patients, Yoder said, “take a longer time.”

‘We are using everything that we have’

If Rush and Chicago’s other five major hospital systems reach capacity, they can send overflow patients to a 3,000-bed field hospital just built by the Army Corps of Engineers inside Chicago’s McCormick Place convention center. Staffing will come from qualified personnel pulled from the suburbs and the surrounding area. Five hundred beds became available last week; the rest will open by the end of April. At that point, the makeshift facility will be one of the largest of its kind in the United States, the state says. The city also signed agreements with downtown hotels to house nurses and doctors working with covid-19 patients if they fear infecting their families.

So far, officials consider this the calm before the surge. Not one Illinois hospital has reached capacity, which makes the state’s greatest struggle so far with the federal government. Chicago and the state are pulling supplies from the state’s stockpile while Gov. J.B. Pritzker (D) has been sharply critical of the Trump administration, charging that it has denied needed supplies to his state. He said he asked for N95 masks but received surgical masks, and he requested 4,000 ventilators but got just 450. Pritzker told CNN that Vice President Pence told him Illinois needed only 1,400 ventilators.

Pritzker said Illinois is particularly vulnerable because it borders Iowa, which has no stay-at-home order, and Missouri, which only recently imposed one — a situation Pritzker attributed to a rise of cases in southern Illinois near St. Louis.

President Trump has attacked Pritzker, saying “he’s always complaining.”

In an interview with The Washington Post on Saturday, Allison Arwady, Chicago’s public health commissioner, said the local stockpile was designed “to serve Chicago and then be supplemented” by the federal stockpile.

According to state data, 1,198 ventilators from the city’s stockpile are in use, and 57 percent are still available. But with about 25 percent of coronavirus patients on ventilators, the need for more is becoming urgent, she said. To date, her office has already pulled ventilators from local zoos, veterinary hospitals and surgical outpatient centers.

“We are using everything that we have,” she said. “But when we look at our models, we need more.

“We anticipate we are going to need more even in the best-case scenario than we have right now. I spend a lot of time trying to convey that sense of urgency to the federal government,” she said.

“We took our part really seriously locally. We really need this, and we need it soon.”

Working against the peak

In a glass-walled boardroom in Rush’s professional building, the system’s top doctors and department heads gather at 9 a.m. on a recent morning to comb through the daily numbers on giant overhead screens. The data tracks covid-19’s journey as it moves through the city, the state, the United States and the world.

They discuss how medical staff members can protect themselves, profiles of certain patients, how Illinois compares with other hot spots around the United States, particularly New York and California. The internal briefings, which take place twice a day, are intended to expedite decision-making, but they are also helping Rush prepare for the inevitable surge in Illinois, which Pritzker said is likely to happen later this month.

If Chicago’s stay-at-home order is lifted in May, many worry that residents — eager to get outside in the warm weather — will congregate too fast and too closely, triggering a second outbreak.

Meanwhile, the hallways of the ICU buzz as medical staff, most working five-day, 12-hour shifts, show no visible signs of fatigue, although Betty Tran, a critical-care physician, admits the pace is difficult to sustain.

“I have a 3-year-old, so a 12-hour shift means it’s tough to see her before or after bedtime,” Tran said.

Omar Lateef, Rush’s chief executive, acknowledges the advantage his hospital has over many others because of its design. But he said the greatest resources at Rush are the men and women in the building.

“What really defines your response isn’t so much a building or number of beds you have or supplies you have, it is the staff and the culture of institution,” he said. “What we found is our staff is not only willing to work, they are volunteering. We have a tremendous list of people trying to get in and help. From the security to the front-door staff to the ICU, there’s not a member of our team not willing to stand up.”