MANILA - Dr Greg Macasaet, an anaesthesiologist in the Philippines, knew his time was up.

"If they intubate me and place me on a ventilator, then the game is almost over," he said in a text message to a fraternity brother.

He and his wife, Evelyn, also an anaesthesiologist, chose to stay at their posts as the first of the patients with signs of infections from a deadly coronavirus outbreak began to roll into their hospital, the Manila Doctors Hospital, one of the biggest in Manila.

Soon, both found themselves infected as well. Within days, Dr Macasaet's condition deteriorated.

He saw the signs. When he learnt his doctors would run cutdown lines - in which a tube is inserted into a vein in an emergency procedure - and central tubes through him, he wrote, "then the game is almost over".

His final thoughts were of his wife, who was also fighting for her life, and his son, who has autism.

"Raymond (his son) needs financial and emotional care for the rest of his life, something I may no longer be able to fulfil," he said.

He asked a bishop to administer his last rites. But by the time the bishop was told, he had already been intubated.

At 4am, on Sunday (March 22), he died.

He was not the only one. At least four more doctors at other hospitals died after they came in contact with patients who were carrying the virus.

Two of them had dealt with the same patient who lied about her travel history.

Health workers in the front line of a war against a deadly coronavirus now racing across the Philippines are under siege. Patients are flooding hospitals, even as masks and other protective gear and hospital beds run out.

The Medical City hospital, which has about 800 beds, said it had 18 patients on Monday who tested positive for the coronavirus. Six had already been hooked up to ventilators, and five more were in critical condition.

It said it has 64 suspected cases, and 137 of its staff are currently in quarantine.

"Unless we are able to move the new patients to other hospitals, our healthcare delivery system is going to break down," said the hospital's president Eugenio Jose Ramos.

St Luke's Medical Centre said its two upscale hospitals in Manila could no longer take in any more patients with Covid-19, the disease caused by the virus.

"Both hospitals have already exceeded maximum capacity and admitting more Covid-19 patients will seriously impact our ability to deliver the critical level of care and attention patients need at this time," it said.

The hospitals are treating 48 confirmed cases and monitoring 139 more who may have the virus. Nearly 600 hospital staff, meanwhile, have been quarantined.

The Makati Medical Centre, another top hospital in Metro Manila, home to more than 13 million, said it also can longer take in any more patients. It currently has 70 confirmed and suspected cases that include some of its doctors, nurses and nursing aides.

It said it "has reached its threshold in its capability to respond to more Covid-19 patients".

The Philippine Heart Centre is also asking patients to go elsewhere.

"We are a cardiac centre. We have a lot of heart cases. These are all high-risk patients.

"We hope that they will have mercy and not go here," Dr Joel Abanilla, the hospital's executive director, said in a radio interview.

Many other hospitals have shut their outpatient departments, and most have stopped accepting non-emergency cases.

"The Philippines is not ready for this. We never were," Dr Ronnie Baticulon, an associate professor at the University of the Philippines College of Medicine, wrote in a commentary for CNN Philippines.

A 2018 study showed that the Philippines had 101,688 hospital beds distributed across 1,223 hospitals.

If just 1 per cent of the country's population of roughly 107 million catches the virus, "it is easy to see how our hospitals will be quite easily overwhelmed", said Dr Baticulon.

A top hospital administrator said most hospitals also do not have enough mechanical ventilators.

The largest and most well-equipped hospital has, at most, just 22 ventilators.

Even more critically, hospitals are running out of personal protective equipment, or PPEs, for their medical staff.

One Manila hospital put out a call for hazmat suits, masks and face shields after its stock dipped to just 98 PPEs in total. A typical hospital dealing with an outbreak runs through at least 100 of these each day.

A small hospital in Los Banos city, two hours north of Manila, was repurposing grocery and garbage bags and plastic water containers as PPEs.

Front-line health workers are picking up the slack. But it is taking a heavy toll on them, as their ranks, already stretched, are further thinned, and they have to worry about their own families.

At least six doctors are listed as critical and over a thousand health workers have been quarantined in Manila alone.

"These days, I worry about my mother, as she cries when she opens the gate to see me off to work. I worry about the way my father coughs... When I'm not with them, I worry that they may be keeping their symptoms a secret, if only to minimise my stress.

"As I come home from work, my concern is that I may bring an infection they won't be able to handle," Dr Raf Gavino, of East Avenue Medical Centre, told the Philippine Daily Inquirer.

For those who tested positive and survived, the crisis is existential.

"I cried. I wasn't ready to die. My child still needs me. There was still a war I had to be in," Dr Grace Caras-Torres, an obstetrician at St Luke's who was "Patient 194" in the Health Ministry's list of confirmed cases, said in a Facebook post.

She said she was not just fighting the virus, "but also to keep my sanity".

Yet, most of the country's health workers called on to report for work remain on the front line, despite the risks.

At 64, Ms Alita Gonzales still goes to the Philippine General Hospital, where she works as a nurse, every day.

She knows she's among the most vulnerable, given her age.

"But we took an oath," she said.