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Christina Paz was typing up notes about a patient she'd just seen at Centro San Vicente, El Paso's largest community health center, when an email from Washington showed up. "Lord," she thought as she read it at the clinic's nursing station. "Oh, my God."

The brief email told Paz, a nurse practitioner who is the clinic's chief executive officer, that at 11:59 p.m. on March 22 the federal COVID-19 Uninsured Program would stop accepting claims for testing and treating for the deadly virus on patients who had no way to pay their medical bills.

On the Wednesday afternoon when Paz opened the federal notice, that deadline loomed just six days away. For a clinic where nearly two-thirds of patients are classified as "unfunded," the $252,000 the federal program has sent Centro San Vicente has been a lifeline as its staff treated more than 2,000 patients for COVID and tested thousands more.

Now, the health center blocks from the Rio Grande is one of more than 50,000 providers of health services nationwide that have run out of time to claim reimbursement from the Department of Health and Human Services for coronavirus testing and care of those without health coverage. And another deadline nears — April 5 — to submit charges for vaccinating the uninsured.

The wind-down of the uninsured program is among the first concrete casualties of a decision by Congress this month to exclude about $15 billion in pandemic relief from a large spending plan adopted for other parts of the government and the Ukraine war.

The Biden administration has been trying to draw attention to the consequences if lawmakers continue bickering over whether to provide more coronavirus aid. The White House and health officials say the government will not have enough vaccines to give every American a fourth shot to protect against the virus, if federal regulators approve the additional booster, and soon will lack money to buy additional monoclonal antibodies to treat coronavirus infections.

Those pandemic-fighting hindrances could lie in the near future. The uninsured program already is ending.

Since it was created in spring 2020 as one of several pools of pandemic aid for health care providers, the uninsured program has provided more than $20 billion in reimbursements to medical labs, hospitals, doctor's offices, pharmacies and clinics. But as it winds down, its absence — unless Congress acts — will be felt most keenly in the health care system's safety net, focused on patients who have no health coverage. Often, those patients are low-income Black Americans or Latinos whose communities have been scarred by the greatest illness and death from the pandemic.

They are places like Harris Health System in Houston, which runs Ben Taub and Lyndon B. Johnson hospitals and a network of clinics. Of more than 16,000 patients with COVID-19 admitted to one of those hospitals or treated by a Harris facility as outpatients, 47% have been uninsured.

Without the federal program, "there is no way we would have been able to care for the number of patients we've cared for," said Esmaeil Porsa, Harris's chief executive officer. At one point, COVID-19 patients filled 22 of the 23 intensive care beds at LBJ, the smaller hospital.

"I was basically running a COVID hospital," Porsa said.

When the initial pandemic relief laws provided money to health care providers, safety-net facilities were not helped much at first. Trying to get money out quickly, HHS began by allotting aid in ways that benefited some well-heeled hospitals that had a lot of revenue or many Medicare patients.

But since federal health officials began setting aside a pool for coronavirus care of the uninsured later that first pandemic spring, Harris has been reimbursed for almost $200 million in services. As a result, doctors, nurses and administrators, stressed by the pandemic's enormity, have been spared the added pressure of considering how to close some other medical services for lack of money. "That's been a huge blessing," Porsa said.

As the program winds down, the financial pressure isn't that intense at the moment, because coronavirus case rates have ebbed, Porsa said. But he said he fears what will happen if a new omicron subvariant, like the BA.2, produces another spike in infections and illness.

"That's the worrying part. We don't have a clue what's in store for us," Porsa said.

At OIC Family Medical Center in Rocky Mount, N.C., fears of another surge weigh heavily as the money is going away.

"I do anticipate it will be a hill to climb to respond adequately," said Reuben Blackwell, president and chief executive of a nonprofit that includes the clinic. In a small city with residents who are largely Black and relatively poor, nearly one-third of OIC patients are uninsured.

Payments through the program and other public pandemic aid allowed the clinic to hire 20 "COVID interns" to fan out into the community to encourage people to get coronavirus tests and shots. Twice a month, they go into day care centers and homeless shelters to give tests. They reach into parts of the community where internet access is scarce, making it hard for people to sign up online for tests or vaccines. OIC has served about 3,800 uninsured patients and been reimbursed nearly $130,000.

In the last few weeks, having heard ahead of time that the uninsured program would end, Blackwell said, 11 of those COVID interns were let go, and three of the remaining workers have been switched to part-time.

With the funding winding down, "it's now all on us to make it work or not. That's scary. We don't have a lot to work with," said Blackwell, who also is a Rocky Mount City Council member. "I just hope that, somewhere in Washington, they have a door locked with some money inside."

According to HHS's Health Resources and Services Administration (HRSA), the agency that has overseen the program, it has been spending about $2 billion a month lately on claims - more than $20 billion since the start. For the past few months, as it became clear the money would soon run out, the agency brought that "burn rate" to the attention of others in the administration who "have been making that very clear to Congress," said an HRSA official, who spoke on the condition of anonymity to be candid.

This month, the White House Office of Management and Budget sent House and Senate leaders a two-page letter laying out "immediate needs to avoid disruption to ongoing COVID-19 response efforts over the next few months." One item was $1.5 billion for the uninsured program - less than the program has been spending in a month.

Advocates for hospitals and community health centers have been pressing lawmakers to pour more money into the program.

Talks are continuing on Capitol Hill, with Republican lawmakers stipulating that they will consider more pandemic aid only if they become convinced there is a clear way to pay for it.

Amid that uncertainty, the HRSA official said agency leaders felt "not great" sending the March 16 email, addressed to "Valued Provider," one of whom was Paz in El Paso.

"HRSA's mission is to address these kind of health disparities, to serve these kind of populations," the official said. "And so obviously, we don't want to be winding down a program if there's a need."

In the meantime, health care facilities that have relied heavily on the money are confronting wrinkles.

One involves a routine lag between when a doctor, clinic, hospital or medical lab provides a service and when the paperwork is submitted to claim reimbursement from the federal government. It is uncertain how much care has been provided for which it is too late to send in a claim.

A second problem is hinted at in the email and involves claims filed before the deadline that have not yet been reimbursed. It says that claims that arrive in time "will be paid subject to . . . availability of funds."

HRSA officials declined to say how much money the uninsured program has in hand to cover reimbursements, even when the claims reached HRSA before the deadline for treatment and testing - or will arrive in early April before the deadline for vaccinations. The official said only that the agency had "received a significant increase in claims leading up to the deadline that are working their way through the system. We are in the process of adjudicating millions of claims subject to the funds that remain available."

At Harris in Houston, the health system is still waiting to be paid for more than $7 million in claims that were pending a few days before the March 22 deadline. Harris is not expecting that all those claims will be paid, said a Harris spokesman, Bryan McLeod.

If the money runs out without Congress providing more, "there are going to be some tough calls" for the nation's health care safety net, the HRSA official said.

Under rules set by the Centers for Disease Control and Prevention, coronavirus vaccines must be given at no charge. The question of possibly charging for coronavirus tests is more ambiguous, and HHS Secretary Xavier Becerra has hinted at that in public. At a recent White House briefing, he was asked whether uninsured people could face bills for coronavirus services if Congress does not act soon.

"We'll exhaust every dollar we have," Becerra said. He said "we're going to do what we can" to keep coronavirus services available "[w]hether it is moving toward allowing Americans to purchase these through other means or secure them through other means, or whether it means getting the support from Congress that allows us to continue to offer those for free."

One company that operates coronavirus testing sites and medical labs, Quest Diagnostics, notified clients last week that, without the ability to bill HRSA, it no longer can provide tests for free to the uninsured, according to a spokeswoman, Kimberly Gorode. Quest will now charge people without health coverage $125 for a PCR test, Gorode said.

Without the federal uninsured program, leaders of health care institutions that serve the poor worry the burden on them could grow.

"If anything, COVID has taught us to be nimble," said David Zaas, chief executive of the Medical University of South Carolina's University Medical Center in Charleston. The medical center is the hub of a health system that has tested 66,000 people who turned up positive for the virus. The hospital has admitted nearly 6,000 people with COVID-19.

If another surge arrives, MUSC, as it is known, will carry out its mission to serve the underserved, said Zaas, a pulmonologist and critical care specialist. Still, he said he fears that other hospitals without that mission could balk at caring for uninsured COVID-19 patients, further straining safety-net hospitals such as his.

At Centro San Vicente, where 80% of patients are Hispanic and most live under the poverty line, Paz said she is still shellshocked by the uninsured program drying up. It was the "huge cushion," she said, that allowed the clinic's four sites across El Paso to avoid furloughs and layoffs as the costs of coping with the pandemic soared.

"We all knew at some point the funding was going to stop. We didn't anticipate it from one night to another. I don't have a strategy how we are going to compensate." In the world of community health centers, she said, "we all wear a million hats. We have yet to have time to sit down and talk."

The one thing she knows, Paz said, is that "COVID is not going away."