VIEQUES, Puerto Rico (AP) — As weeks turned into months, the seats of the small plane began to empty out.

In the beginning, 15 passengers flew from Vieques to the Puerto Rican mainland — refugees from Hurricane Maria. The storm had ruined the only dialysis center on this tiny island, their home; without treatment, the kidney patients would die.

But the thrice-weekly trips have taken a toll on these frail patients. Five have died in this past year from causes ranging from heart failure to cancer, but advocates insist that the very flights that keep the patients alive have hastened their deaths.

The mortality rate is “a high number,” said Angela Diaz, director of the nonprofit Renal Council of Puerto Rico. “We obviously cannot dismiss the fact that these are not appropriate conditions. It’s vital that (the government) take action as soon as possible. … As much as they want to avoid the topic, we have to talk about how we’re still doing this one year after Maria.”

As dire as the situation may be, it could get worse. A mobile unit, purchased by federal officials to provide dialysis on Vieques, is stuck more than 3,000 miles (4,800 kilometers) away, in California; the Renal Council, which is paying for the dialysis flights, says it will run out of money to do so by month’s end.

“If they take away our flights, we will end up dying,” said Elias Salgado, a 56-year-old renal patient who is diabetic and suffers from high blood pressure. “There are not many of us left.”

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The Vieques dialysis center was located in the island’s only medical clinic. The building still stands, though it is heavily damaged and strewn with horse manure. Weeks after Maria hit, health officials declared it contaminated and ordered that it be demolished.

Other health services were moved to a temporary shelter, but dialysis could not be performed there.

At first, the Federal Emergency Management Agency assumed responsibility, flying the patients by helicopter to San Juan. After a month, FEMA withdrew to take on other missions; nonprofits, including ViequesLove and Americares, picked up the bill. For a while, the patients traveled by ferry — a more arduous trip because the boats sometimes break down or fail to leave on time, and there is no way to reserve seats. They would show up early, and hope for the best.

Since March, the Renal Council has been paying $3,900 a week for the flights, $6,000 a month for a paramedic to accompany the patients and $2,500 a month to feed them.

The flights take just 20 minutes. But the journey is far longer.

The patients wake up before dawn, wait at the airport for the plane to arrive, clamber aboard and then, once they reach the mainland, wait for transportation to the clinic. There, they sit for four hours as their blood flows through a filter and returns cleansed of toxins. Then they repeat the same routine to get home, arriving about 12 hours after they started their day.

“It’s exhausting,” Salgado said.

“You don’t get used to this,” chimed in Edwin Alvarado, a 59-year-old dialysis patient who also has high blood pressure and had open heart surgery five months after Maria.

Before Alvarado got a chance to sit down at the airport’s waiting room in Vieques on a recent Saturday, the paramedic intercepted him. He wrapped a cuff around Alvarado’s bicep and took his blood pressure: “It’s high,” the paramedic warned, “180 over 110.”

Alvarado shrugged. Like Salgado, he’d love to move to the U.S. mainland and live close to a dialysis clinic, but he has nowhere to stay and cannot afford to leave Vieques and find somewhere new to live.

Salgado has another reason to stay: He’s on Puerto Rico’s transplant list.

“I could be called at any moment,” he said.

Some of the patients knew each other before the storm; Vieques is a small island, with about 9,000 people. As months progressed, they began to feel like a small family, complete with quibbling, especially about those who complain too much.

Both men cheered up as a third dialysis patient, Leyla Rivera, strolled into the airport and lobbed small packets of vanilla cream cookies at each of them. She sat down with a sigh.

At 45, she is one of the youngest patients on the flight, and even she struggles to find the energy.

“Sometimes you come out of treatment dizzy, vomiting,” said Rivera, who is seeking a spot on the transplant list. The mother of an autistic child, she is forced to skip two days of work every week because of the flights.

Before 7:30 a.m., the pilot announced he was ready. The patients made their way slowly down a ramp and took their favorite seats on the plane. They lapsed into silence as the small engines roared.

Less than an hour later, an ambulance with flashing lights pulled up to the airport. Inside lay 42-year-old Sandra Medina, another dialysis patient with diabetes and high blood pressure. Doctors amputated half her leg after an infection that worsened months ago.

She smiled slightly and confided that she’s a nervous flyer, and that sometimes she loses hope.

“We go through a lot,” she said.

Two paramedics wheeled her out to the runway and lifted her into another special gurney inside a small plane as she turned her head and looked out the window.

“Behave,” one airport worker told her as he smiled and closed the plane’s door.

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Salgado’s doctor, Jose Figueroa, worries about the effects of such exhausting travel. He likens it to insisting that someone walk home after running a marathon.

“Eventually those patients, who already are fragile, will keep worsening,” he said. A year of this, he said, was “unacceptable.”

Survivors of those who have died over the past year acknowledge that their loved ones were very sick, but they believe they need not have perished.

Argeo Caraballo, 70, died of heart failure on Feb. 13. “The trips were way too exhausting,” said his daughter, Gladys, who traveled with him and found the trips grueling, as well. “He completely deteriorated after Maria.”

Hector Serrano, 57, was co-pastor of a Vieques church. He died in mid-August of cancer and other ailments. Said his sister, Magali Rivera: “It’s a crime what they’re doing to these renal patients. … He (Hector) would have been by our side for longer.”

Peter Quinones, spokesman for the Puerto Rican health secretary, Dr. Rafael Rodríguez Mercado, did not respond to several requests for comment on why Vieques still has no dialysis center. Or why the department has not paid to have the $3 million mobile clinic FEMA purchased delivered to Vieques. Legislators in Puerto Rico have pledged that the clinic will soon arrive, although they have not said when.

Daisy Cruz, deputy mayor of Vieques, said she is in constant communication with FEMA officials but receives limited answers from local health authorities. She said she has proposed rehabilitating an old pharmacy so it can be used for dialysis, but she has not heard back from Fresenius, the company that had operated the Vieques clinic.

Luis Emanuelli, a vice president at Fresenius Kidney Care, said the company has long been ready with the equipment and staff needed to resume treatment in Vieques under an agreement with Puerto Rico’s health department, which has to provide a licensed facility.

The company is committed, he said, to “resuming operations as soon as there is a suitable location for us.”

But patients say they have waited long enough and want Puerto Rico’s government to deliver on its promises.

“It’s an injustice to have us like this” — flying back and forth for treatment — “when they can put a clinic here,” Medina said.

Meanwhile, money is running out to pay for those flights.

“Where is the conscience? Where is the humanity?” Cruz asked, tearing up. “It’s always, ‘We don’t have the money, we don’t have the money, we don’t have the money.’ But they’re putting at risk lives that we could prolong.”