One by one, men and women in masks stepped quietly behind a set of white curtains at the far end of the Jones-Harrison Residence nursing home in south Minneapolis and prepared to be tested for the coronavirus.

They tilted their heads back and winced or even moaned as a nurse inserted a long cotton swab up their nostrils. "One, two, three, four, five ...," counted the nurse, Julia Marek, as she twisted the swab around in a woman's nose. "You're done!"

In the past few months, coronavirus testing has become embedded in the daily routines of senior living communities across Minnesota. Large nursing homes that as recently as May struggled to find single tests are now collecting hundreds of swab samples a week from residents and staff, converting lobbies and social rooms into makeshift testing sites. The widespread swabbing represents a dramatic departure from the early days of the pandemic, when silent outbreaks would spread for weeks through buildings without detection because of inadequate testing.

Yet the rapid expansion of coronavirus testing in senior care communities has put greater pressure on an already stretched system, particularly as cases of the coronavirus surge across the state and the nation. More than five months into the pandemic, testing results are being delayed by a shortage of vital supplies and backlogs at the private laboratories that process thousands of samples each day. Nursing homes say the typical turnaround time is two to three days. But some facilities are reporting delays of four to seven days for testing results, which hinders their ability to isolate infected residents and warn people before they infect others.

Across the state, nursing home and assisted-living administrators said they are worried that a combination of factors — including the reopening of schools and the alarming resurgence of the virus in the community — could stretch the testing system beyond its limits.

This could lead to more prolonged turnaround times and potentially render the tests useless in containing the virus in their facilities, some administrators warned.

"Minnesota has come 180 degrees from where we were in May, but [testing] could be better," said Amanda Johnson, a nurse and vice president of clinical operations at Tealwood Senior Living, a Bloomington-based company that operates 30 senior facilities in Minnesota. "I'm very concerned that we still don't have the capacity to handle the volume of testing that's needed."

Minnesota Department of Health officials said the agency has received reports of long turnaround times and delays at some facilities using out-of-state laboratories and added that some of the delays appear to stem from a nationwide shortage of testing supplies.

Because of critical supply shortages, Mayo Clinic's national reference lab in Rochester recently had to reduce its testing capacity by nearly half, from 20,000 tests a day to 10,000 to 12,000 tests. However, Mayo is buying three new testing platforms that will expand its capacity and make its laboratory less sensitive to shortages from one supplier. That addition will boost Mayo's capacity to as many as 30,000 COVID-19 diagnostic tests per day by the end of this month.

"Even 30,000 tests a day may sound like a lot," said Dr. Bobbi Pritt, Mayo's chair of clinical microbiology. "But then you think of all the people who live in Minnesota, and that's really a drop in the bucket."

In early May, amid soaring infections, Gov. Tim Walz made expanded testing a key part of a "battle plan" to address the mounting death toll from COVID-19 in long-term care facilities. The Health Department even deployed the Minnesota National Guard to help with testing. Since then, the agency and the Guard have provided a broad range of testing support, helping 85,000 staff and residents be tested for the virus at 485 long-term care facilities statewide.

The dramatic ramp-up of testing by the state marked a turning point. For the first several months of the pandemic, facilities had largely been reacting to individual cases when they arose and testing only those who appeared sick, even though many people infected with the virus do not show symptoms. The deployment of the National Guard enabled many long-term facilities to test everyone who lived and worked in their communities for the first time. That helped them isolate infected patients and establish a more consistent testing regimen, long-term care providers said.

As recently as May, many nurses and aides who worked in senior homes who suspected they were infected had to get coronavirus tests on their own and find a way to pay for it. In some cases, staff would be turned away when they tried to get tested at a private clinic, or they would be forced to quarantine for days at home while awaiting results. Now testing has become as routine as picking up a paycheck: Swabs are collected during work hours, often by co-workers and with minimal hassle.

"Is it fun to get a cotton swab stuck up your nose? No, it's not fun. But it's one of the most powerful tools we have in the fight against COVID," said Annette Greely, president and chief executive of Jones-Harrison Residence, which now conducts more than 250 tests a week of residents and staff.

Even so, Minnesota's 2,000 senior living communities are still dependent on a complicated network of private and public laboratories that operate their own testing systems. In recent weeks, as the demand for testing has surged along with new infections, the capacity of these laboratories has become strained. Many laboratories are still able to process tests within 48 hours, facility administrators said. But some are taking much longer. Some facilities said they are sending samples as far away as Kentucky or Utah because of supply constraints at labs in Minnesota.

At times, the patchwork testing system can be a "clerical nightmare," said Johnson of Tealwood Senior Living.

Like many long-term care providers, Tealwood ramped up its testing capability in May, and now conducts nearly 2,500 tests a week at its facilities in Minnesota. To process this large volume of tests, Tealwood turns to eight to 10 laboratories. But each laboratory uses its own equipment and chemicals, and turnaround times can vary from week to week based on supply constraints. Sometimes the results come back in batches spread over several days or are sent late at night by fax after many staffers have gone home.

"The way these tests are processed by the labs can make them very difficult to track," Johnson said.

The supply shortages have also created unexpected delays and administrative headaches.

For instance, in late July, Maple Lawn Senior Care in Fulda, Minn., a senior living community in the southwest corner of the state, arranged for all its residents and staff members to be tested for the coronavirus for the first time. Staff and administrators at the senior community spent several weeks preparing for the event and had arranged for the Minnesota National Guard to help collect the samples. Dozens of workers who had the day off had arranged to drive in to the facility to get tested.

However, the crucial testing supplies from the laboratory did not arrive until the night before testing. When staff opened the boxes the next morning, they made an unpleasant discovery: The boxes lacked enough of the chemical reagents needed to detect whether the coronavirus is present in a sample. With Guard officers already on-site, the facility had to inform residents and staff that testing would be spread over several days as the missing supplies arrived.

Eventually, the facility received good news: All 80 staff and 90 residents tested negative for the coronavirus.

"Trying to coordinate a facility-wide test requires a lot of coordination, so any delay is frustrating," said Arlan Swanson, administrator and chief executive at Maple Lawn. "Somehow someone in the system must have known that the supplies were not going to arrive, but it was not communicated to us."

Some public health experts said problems with obtaining timely tests will persist until new, more rapid tests are developed.

They are holding out hope for technology, known as point-of-care testing kits, which would enable facilities to process their own tests and detect cases of the coronavirus without having to send samples to distant laboratories.

"Everyone would love more rapid tests that have a high reliability, but that's largely beyond our control," said Greely of Jones-Harrison. "That's in the hands of the scientists and the laboratories."

Staff writer Jeremy Olson contributed to this report.