"The unauthorized immigrant population has become more settled in recent years, and as a result is aging," said Mark Hugo Lopez, director of global migration and demography at the Pew Research Center in Washington. (The Pew Charitable Trusts funds both the Pew Research Center and Stateline.)
Estimates vary on how many undocumented immigrants lack insurance. The Kaiser Foundation estimates 39 percent of undocumented immigrants are uninsured, while the Migration Policy Institute, which analyzes U.S. Census data, estimates as many as 71 percent of undocumented adults do not have insurance.
Like Marcos, older undocumented people tend to be poor. The Affordable Care Act doesn't cover them, and they don't qualify for Medicaid, Medicare or Social Security, even though many pay taxes. They can buy private insurance, but few can afford it.
That means most must turn to emergency rooms or community health centers, federally funded clinics that provide primary health care to poor people on a sliding scale, regardless of their immigration status. But community health centers were originally created to provide maternity care to women and aren't equipped to provide extensive care to undocumented seniors, Wallace said. And because Congress has yet to fund them this year, their future is precarious.
Leighton Ku, professor and director of the Center for Health Policy Research at George Washington University, said immigrants, both authorized and unauthorized, are much less likely to use health care than are U.S. citizens. This is partly because of language barriers, and partly cultural, Ku said. "They get sick, and grin and bear it." Until, that is, they're quite ill.
Many also fear running afoul of immigration authorities, health officials say, which means that by the time they get to the doctor, they're even sicker.
"Their numbers are going to grow and we're going to have an epidemic on our hands," said Maryland state Del. Joseline Pena-Melnyk, a Democrat whose district has one of the highest rates of undocumented immigrants in the state. "Who's going to pay for it?"
Already, there have been some indications as to who will have to foot the bill. A 2014 report by the Texas Medical Association found that undocumented immigrants with kidney disease face considerable barriers to care. By the time they do get help, they need dialysis, costing Texas taxpayers as much as $10 million a year.
Many cities have tried to step in. A 2016 Wall Street Journal story noted that 25 counties with large undocumented populations provide some non-emergency health care to these immigrants, at a combined cost of what the paper estimated is more than $1 billion each year.
Washington, Los Angeles and San Francisco are among the places where immigrants can usually get access to some kind of routine care, no matter their immigration status, thanks to locally funded health care programs.