As many as 16 million low-income Americans, including millions of children, are destined to fall off Medicaid when the nation’s public health emergency ends, as states face a herculean mission to sort out who no longer belongs on rolls that have swollen to record levels during the pandemic.

The looming disruption is a little-noticed side effect of the coronavirus crisis, and it is stoking fears among some on Medicaid and their advocates that vulnerable people who survived the pandemic will risk suddenly living without health coverage. For the Biden administration — which will make the decision on when to lift the health emergency — there is the potential political stain of presiding over a surge of poor, newly uninsured Americans, depending on how things go once states resume checking which Medicaid beneficiaries still qualify.

“The main concern I have is people are going to be cut off for reasons that have nothing to do with their eligibility,” said Gordon Bonnyman, a staff attorney for the Tennessee Justice Center, a nonprofit working for affordable health care. “Either they drop the ball, or the state drops the ball.”

The unprecedented work that lies ahead will wind down a profound, temporary change Congress made to Medicaid, the nation’s largest public health insurance program, early in the pandemic.

The first coronavirus relief law, in March 2020, offered states a bargain to help them cope with the sudden spurt of Americans losing jobs and health benefits that accompanied the worst public health crisis in a century: The federal government would give states extra money to help pay for Medicaid if they promised not to move anyone off the program as long as the emergency lasted.

Every state accepted the bargain at a moment when few imagined that, two years later, the pandemic — and the public health emergency the Department of Health and Human Services has been renewing every 90 days since the coronavirus’s first winter — would still be present. In that time, Medicaid caseloads have jumped about 22 percent nationally as new people have joined and no one has cycled on and off the rolls. The nearly 78 million Americans on Medicaid as of September, the latest figure available because federal tallies run months behind, are the most since the program began as a shared federal-state responsibility in the 1960s as a pillar of President Lyndon B. Johnson’s War on Poverty.

Once the federal emergency is lifted, every state will need to reassess its entire bloated roster. Many of the people who will be removed from the safety-net insurance probably will qualify for private health plans, according to Biden administration officials and health-care researchers and advocates.

But large questions hover over how many beneficiaries whose incomes have risen above Medicaid’s eligibility thresholds will simply disappear instead of sliding over to other insurance. And it is unclear how many who remain eligible will be removed from the program improperly.

For Biden health officials, helping states get ready for this enormous task — dubbed “unwinding” from the health emergency — has been a preoccupation for several months. They have sent states a detailed punch list of recommended steps to take in preparation, dispatched letters spelling out federal expectations and continued to confer often with each state.

“This is at the top … of our priority list,” said Daniel Tsai, who oversees Medicaid in HHS’s Centers for Medicare and Medicaid Services. “We intend to and are using all levers available to us to make sure we are connecting people with coverage.”

Still, each state runs its own program. Interviews with state officials, health-care advocates and policy specialists reveal deep differences over how much time, effort and money states are devoting to this work. In certain places, advocates warn that problems — including outdated addresses for renewal notices and error-prone computer systems — could undermine some of the poorest Americans’ ability to afford care.

Brad Ledgerwood knows the possibility of errors, and he knows the stakes. Ledgerwood lives in Cash, Ark. — a “spot in the road,” as he puts it, with 342 residents in the Arkansas Delta. Nearly half live in poverty.

Ledgerwood was born with cerebral palsy. “I can do everything I want to do as far as my mind,” he said. He has been on Cash’s city council for nine years. “My problem is my physical ability,” he said. “I cannot do anything physical by myself. My mom and dad are my hands and feet.”

At 40, he has been on Medicaid more than half his life, since he turned 18, under a part of Arkansas’ program that covers care at home to help people like him stay out of nursing homes. His mother, Ann, quit her job as a county appraiser to be his caretaker. Medicaid covers the cost of eight hours of care a day, adding up to about $62,000 in benefits. Ledgerwood has that amount of coverage — three times what he would get otherwise — because he is grandfathered into an older version of the program for as long as he remains eligible.

Starting in November, Ledgerwood said, the first of four notices from the state arrived in the mail, telling him that he no longer qualifies for Medicaid — but that his benefits would continue for now because of the public health emergency rules. The notices have kept coming even after a county nurse paid him a visit in January and confirmed the services he needs. They have kept coming even after he and his Legal Aid lawyer called the state and were assured that a computer glitch caused the letters.

If notices keep coming once the health emergency ends, and he is dropped from Medicaid even temporarily, he will not return to the same level of benefits. Ledgerwood said he worries that he and his parents couldn’t live on his father’s pay from a Jonesboro factory that makes Delta truck toolboxes. If that happened, Ledgerwood fears, his mother might need to go back to work, and he might land in a nursing home like the one 60 miles away where his grandfather spent his final years — rather than rolling up and down the road in his wheelchair, greeting neighbors when the weather is fine.

Asked about such computer-generated errors, Cindy Gillespie, secretary of Arkansas’ Department of Human Services, said, “If there is something going on, we want to know and get it fixed.”

Ledgerwood’s Legal Aid lawyer, Trevor Hawkins, questions whether Arkansas is equipped to handle the work ahead. Already, the state has amassed a large backlog of Medicaid applications. The legislature has not provided additional money for that or for the unwinding, but Gillespie said the extra money from the federal government allowed her department to hire a contractor a few months ago to help it get caught up. And the state’s Medicaid director, Dawn Stehle, said she has been convening weekly internal meetings since the fall to prepare for the unwinding.

Arkansas’ Medicaid enrollment has grown from 927,282 in early 2020 to nearly 1.1 million by January. Because the state has continued eligibility reviews through the pandemic, it believes that more than 220,000 people no longer qualify but are still getting benefits. Starting this month, a nonprofit working with the state will try to call those people to check their phone numbers and addresses.

But Hawkins pointed out that Arkansas passed a law last year that requires the state to carry out its Medicaid eligibility decisions within six months of when the unwinding begins — half the time the Biden administration says states should take.

A recent Ohio law requires a more tightly compressed period: two or three months, depending on how long someone has been on Medicaid. Michigan lawmakers are considering something similar.

Advocates predict that if Medicaid programs move hastily, they will have too many erroneous addresses and call centers will be overwhelmed. And they fear that computerized eligibility systems, which can be error-prone in certain states in ordinary times, will be unable to spit out accurate renewal decisions. Compounding the problem, many states’ Medicaid agencies are short-staffed, having lost workers during the pandemic, while some employees hired lately have no experience at handling renewals.

Biden health officials are telling states to take their time, urging them to use a full year to help ensure that renewals are handled accurately — double the six months the Trump administration had said would be allowed.

But there is a catch. The extra federal money will last no more than three months after the public health emergency ends. After that, states will have to shoulder a bigger portion of the costs associated with their swollen Medicaid caseloads while finishing the unwinding.

The administration and congressional Democrats have tried to create a cushion to deter states from unwinding quickly to save money. The cushion, part of a far-reaching social policy bill, would ratchet down the extra federal payments more gradually. But the legislation, called the Build Back Better act by its enthusiasts, is stalled on Capitol Hill.

One state’s experience with a similar insurance program offers a preview of what can go wrong if states move too fast. In Utah, a federal insurance program for children from working-class families was initially handled in a fashion similar to Medicaid, with all children kept in the program during the pandemic. Last year, the state reversed course on the Children’s Health Insurance Program — widely known as CHIP — scrambling in two months to send renewal notices and make new eligibility decisions. More than 40 percent of Utah children on CHIP were dropped.

“It ended up being a disaster,” said Matt Slonaker, executive director of the Utah Health Policy Project, a nonprofit that fought for several years to expand Medicaid in that state and coaches Utahns to sign up for Affordable Care Act marketplace health plans. He fears Utah will not take enough time for the Medicaid unwinding, either.

A big wrinkle in planning is that it is unclear when that unwinding will begin.

The latest extension of the health emergency runs through mid-April. States are assuming that HHS will continue it, because Biden health officials have promised to give 60 days’ notice before its end, and that has not happened.

The Biden administration has no official forecast of how many people are likely to fall off Medicaid. Tsai and other policy experts cite research by the Urban Institute, a Washington think tank, that began estimating late last year how many people would lose coverage after the health emergency stops. The latest updates predict that more than 14 million beneficiaries could lose Medicaid if the emergency expires midsummer, and nearly 16 million if it ends early in the fall.

Matthew Buettgens, a senior fellow at the Urban Institute who is the study’s lead author, said that no matter when it begins, “the systems themselves, both human and computer, weren’t designed to handle that volume.”

Meanwhile, a new study by the Georgetown University Health Policy Institute’s Center for Children and Families estimates that 6.7 million children insured through Medicaid will lose coverage.

“This could be disastrous for children — especially Black and Latino children,” whose families are more likely to be poor, said Joan Alker, the Georgetown center’s executive director and the study’s main author.

Tsai and Jonathan Blum, chief operating officer of the Centers for Medicare and Medicaid Services, known as CMS, said the agency is working with states’ Medicaid programs more intensively than ever, coaching them to avoid a widespread loss of eligible people and find smooth paths to other coverage for those who no longer qualify.

Some states are embracing federal advice far more than others.

In California, where Medi-Cal is the nation’s biggest Medicaid program, the state took the rare step starting in December of sending letters to all 14.4 million beneficiaries to test whether they reached their intended recipients, said Jacey Cooper, Medicaid director in the state’s Department of Health Care Services. The program has given California’s county social services departments, which are in charge of renewals, scripts to answer callers’ questions in 19 languages. To do even more outreach, California is giving extra money to federally funded “navigators” — community workers who help consumers sign up for ACA health plans and steer others toward Medicaid.

“It definitely keeps me up at night,” Cooper said, “because I want to ensure that people who need coverage can remain on coverage.”

In New Mexico, which has the highest proportion of residents on Medicaid in the country, the state has told the three insurers that provide Medicaid managed-care plans that they must offer ACA health plans, too, to make it easy for people to switch over, according to Nicole Comeaux, the state Medicaid director. And Gov. Michelle Lujan Grisham (D) persuaded the legislature to devote $35 million to help people with the transition from Medicaid, including to pay premiums for a month for anyone who moves into a marketplace plan.

In contrast, Jodi Ray, director of Florida Covering Kids & Families, has been sending emails since the fall to Florida’s Department of Children and Families, which runs Medicaid there. She keeps suggesting that her squad of navigators, the nation’s largest, help with the unwinding.

“We are on the ground,” Ray said. “I keep trying to offer up: Here is a strong team that can help.” She said she has not heard back.

Katy DeBriere, legal director of the nonprofit Florida Health Justice Project, said the state’s computerized eligibility system is antiquated and predicted that “it is going to be a huge problem.”

Florida’s Department of Children and Families did not respond to requests for comment about its preparations.

CMS has latitude to penalize states if they shirk federal rules for the unwinding — but has not so far. Tsai said it will be better able to assess how prepared states are once it is clear when the unwinding will begin.

Bonnyman, with the Tennessee Justice Center, is one of many advocates around the country who are nervous. “What scares me is this system was not working great when they lifted the needle off the record,” Bonnyman said of Tennessee’s Medicaid renewals. “We won’t know what’s going on … until it fires back up. We just have to wait for people to be hurt.”

From his wheelchair in Cash, Ledgerwood has the same anxiety.

“I think a bunch of people will be getting cut off for no reason because the computer messed up,” he said.

“I know how to fight it,” said Ledgerwood, who has just been appointed to a Medicaid consumer advisory board that Arkansas is creating. What he worries about, he said, “is people who don’t know to call a lawyer and don’t know their rights. Some people will fall through the cracks.”