Hospitals that should be saving people are instead unable to provide care.
At the Canovanas Medical Center, doctors face a lack of supplies. Dr. Norbert Seda said they were running out of fuel for the generator and had only two or three days of medicine and supplies left.
While residents were prepared for the storm's arrival and mercifully few were killed directly by the hurricane, the need for medical treatment is getting greater.
"We've seen a lot of trauma," Seda said. "We need medication, antibiotics, tetanus shots, we've seen a lot of trauma basically, (we need) antibiotics and medication for hypertension."
He's not encountered people dying because of a lack of power and supplies -- yet.
"It's coming. When there's a shortage of water and sanitation issues, it will come out. We are expecting something like that to happen."
Lack of fuel is the key problem at San Jorge Children's Hospital in San Juan, according to its executive director, Domingo Cruz Vivaldi.
"We are dealing with a crisis right now. The hospital is needing diesel every day -- 2,000 gallons a day. Yesterday, we ran out of diesel at 6 a.m. and we were without electricity at the hospital from 6 a.m. through 2 p.m. Eight hours without electricity."
Without power, lifesaving machines like ventilators have to run on emergency backup power.
Fears for the future are playing out across Puerto Rico.
Misery is stalking each and every one
of the more than 3 million Americans there.
San Juan Mayor Carmen Yulín Cruz sees a growing need for help
for increasingly desperate people.
"We are finding dialysis patients that have not been able to contact their providers. We are having to transport them in near-death conditions," the mayor said. "We are finding people whose oxygen tanks are running out because our small generators now don't have any diesel."
Most alarming are the SOS messages, she said, "the ones that say 'Can anyone hear me?' The ones that say 'I have no more food and I'm out in the street.'"
Yulín Cruz and her teams are out on the streets trying to find the neediest people. But in the mountains south of her city, help is less likely to come.
Combat war veteran Miguel Olivera has less than two days' supply of his lifesaving insulin left
. And even that may spoil in his refrigerator with no power.
The mayor of his town, Javier Garcia, believes help will come from the mainland and the federal government.
The question is when, and whether it will be too late for Olivera and others.
The main airport in San Juan is crippled, barely functioning. Those there are hoping to escape a crowded terminal with no air conditioning. On Tuesday, only 10 flights were scheduled.
Check-in desks were packed with people waiting in line, hoping for a flight off the island. Fans were running, but keeping no one cool. Hopeful travelers sat in chairs on line and others lay nearby, using their suitcases as pillows. A mother rocked a stroller back and forth to try to calm a child.
Until aid arrives, Garcia and his fellows in Aguas Buenas are reverting to an older way of life -- hacking coconuts to eat and collecting water from mountain streams. But that can only sustain so many for so long. Twenty-first century help is needed for many, like Miguel Olivera, who rely on medication. And the situation can so easily get worse -- mosquito-borne diseases like Zika and Dengue fever are very real fears here.
A massive power tower that was toppled in Aguas Buenas will take a helicopter to restore. That's one very obvious problem. But Puerto Rico's power grid was a mess well before the storm and it will be months -- several months -- before electricity is restored across the island.
Generators are now essential -- and essential to them is gasoline. Gas stations around San Juan do have some supply, but the demand is overwhelming.
Long lines of vehicles queue up at the pumps and men with red plastic gas cans wait for up to six hours, hoping to get a few precious gallons. Similar lines grow outside any open grocery store and anywhere that has ice.
It's hot. And it's humid. Temperature were set to rise to the low 90s on Tuesday. Showers are forecast later this week but they will barely make it any cooler.
Puerto Rico's leaders and many of its people say they are resilient, they will survive, they will rebuild.
But signs of desperation are beginning to show.
A reporter climbing out of a helicopter is grabbed in a bear hug by a weeping woman in Quebradillas, a cut-off town. The woman doesn't know who the reporter is, but she is a person from the outside, perhaps someone with news of supplies, who can take a message to family, who can offer something.
From the air, you can see people walking along highways, reaching up, searching for a cellphone signal. Floods, storm debris and the ever-present lack of power mean a fleeting phone conversation may be their only link to the rest of the island for some time.
The same struggle evident in Quebradillas is playing out across Puerto Rico.
Utuado suffered several deaths in the storm itself and saw homes washed away. Rosario Heredia lost her home. She is diabetic and just had surgery. She's still there, hoping for help, from anyone. But so far, no one has come.
Now this community of 30,000 is turning to a pipe, tapped into a mountain spring alongside a highway, for water.
Harry Torres said the water is all they have for cleaning and drinking until help comes. He and his fellow residents are just "trying to survive."
"We're desperate," Torres said.
The situation is dire for those who cannot even make it to that trickling water. The hurricane brought mudslides here, leaving some unable to get to the highway due to blocked roads or lack of gas.
Lydia Rivera has two cars, but no gas and cannot reach that pipe for water. Now she's trying to keep her two grandchildren alive on a ration of crackers and survive on rainwater.
In Yauco, already a remote town, all the roads are blocked. The only way in is climbing up a hill, and over many downed trees.
Coffee growers Gaspar Rodriguez and Doris Velez have lost just about everything they've worked for. But their biggest worry now is how they will survive.
They are in desperate need of food. Most of what they have has gone bad.
In Yabucoa, which took a direct hit, there is no power and residents say they have also been without fresh water for days. The little food in town is being shared by neighbors.
Every single part of Puerto Rico took a hit. From the air it looks brown, not the verdant green of the tropical island it is.
Nothing is normal and there is little sign of when any sense of normality will return -- from schools opening to hospitals being able to care for the sick. Millions don't know when they'll be able to turn on a tap and get water, or flick the switch and have light or cooler air.
San Juan resident Sebastián Pérez showed CNN how he's surviving without running water and power. His fridge is useless for keeping anything cold and he hasn't driven his car since the storm, wanting to keep the gas for emergencies.
"Food-wise it's getting kind of scary," he said. "I'm trying to use as less as I can."
"Because I don't know when it will get better."
CLARIFICATION: This story has been updated throughout to reflect the full last name of San Juan Mayor Carmen Yulín Cruz.