A doctor who treated victims from the US gay nightclub shooting has written a poignant message that he will "never forget" his experience.

Joshua Corsa, a senior surgical resident at Orlando Regional Medical Centre, was working overnight when dozens of people who had been partying at the Pulse nightclub were brought in with gunshot wounds.

When he returned to work the next day, he posted a photo of his blood-stained shoes to Facebook and said the blood would stain him forever, in a post that was shared more than 300,000 times.

"These are my work shoes from Saturday night. They are brand new, not even a week old," Dr Corsa wrote.

"On these shoes, soaked between its fibers, is the blood of 54 innocent human beings. I don't know which were straight, which were gay, which were black, or which were hispanic. What I do know is that they came to us in wave upon wave of suffering, screaming, and death.

"And somehow, in that chaos, doctors, nurses, technicians, police, paramedics, and others, performed super human feats of compassion and care."

Dr Corsa said, in the post that he later appeared to delete, that he would always see the faces of the patients and those who "gave everything they had in those dark hours" when he looked at the shoes.

"There is still an enormous amount of work to be done," he said. "Some of that work will never end. And while I work I will continue to wear these shoes. And when the last patient leaves our hospital, I will take them off, and I will keep them in my office. I want to see them in front of me every time I go to work.

"For on June 12, after the worst of humanity reared its evil head, I saw the best of humanity of come fighting right back. I never want to forget that night."

Nine people died when they were taken to the hospital directly after the shooting, with some arriving with no vital signs.

Since then none have died from their injuries, with the hospital saying the 29 remaining in hospital had a "positive prognosis" including five who were in a critical condition.

Dr Michael Cheatham, the chief surgeon at the medical centre, told Good Morning America he and his staff were learning to cope with the "tremendous tragedy".

Around 200 families headed to the hospital after the shooting, with staff having to break the news to some of them that their loved ones hadn't been taken to the hospital.

"We were trying to reunite families with victims as quickly as we could," Dr Cheatham said.

"The devastating thing was watching family members learn their loved one was not in the hospital and was therefore likely still in the club, unfortunately having died in this incident."