Death comes quickly in the Ebola ward. British nurse Will Pooley is back on duty after a mid-morning break when a colleague calls through for a body bag. Inside, 18 patients, from a three-day-old baby to a 76-year-old woman, are fighting for their lives.

A whiteboard in the small administration room next door charts the progress of each patient: “stable”, “very weak, push oral intake”, “unhappy”. The words “escaped but returned back” are scribbled next to one. Cooled by a floor fan, nurses, doctors and support staff in blue scrubs move through the small anteroom next to the isolation ward to juggle the needs of the desperately ill patients inside as a stream of people knock on the canvas door asking for updates on their loved ones.

Metres away, outside in the street, four Ebola victims lie listlessly on benches in a tent erected to deal with the queues of patients who descended on this clinic in Freetown when Ebola first flared up in the Sierra Leonean capital.

Within half an hour, Pooley emerges from the ward drenched in sweat that has built up inside his protective overalls, mask and goggles. Without a word, he walks to the whiteboard and scrubs out the words “weak, push oral intake” for the patient in bed number six and writes in their place: “Died 12:30”. The girl was 14.

Within minutes, those words are scrubbed out again and replaced with “lab”, short for lab results pending for the new resident of bed number six, a 29-year-old man. By the time Pooley’s day finishes, three more patients will have died.

For the British nurse and his new colleagues, this is business as usual. “We’re averaging eight to 10 corpses a day, some of them dead on arrival; there’s a dead body every hour or two,” he explains later.

Pooley is working for Britain’s King’s Health Partners, which runs the isolation ward at the busy Connaught hospital in Freetown. The first and as yet only British person to contract Ebola, he is back in Sierra Leone, two months after making a full recovery, to resume his role in the fight against the disease, which is now sweeping the capital.

It is a world away from the Royal Free hospital in the affluent north London suburb of Hampstead, where he was treated in a state-of-the-art ward after his own brush with death. After catching Ebola in August while volunteering in another Sierra Leone hospital, Pooley was airlifted back to Britain and treated by some of the world’s top infectious disease experts. The difference in his treatment and those of his new charges is far from lost on him. In Hampstead, Pooley had specialist care from at least a dozen health workers. “Here it’s the reverse; there are more patients than healthcare workers,” he says.

Ebola thrust Pooley on to the world stage, but all he ever wanted to do was get back to Sierra Leone to help fight the “real emergency”. Despite the death toll, Pooley is visibly energised by his work and full of purpose. “You finish a day here and you feel like you have really done something.”

His boss, Marta Lado, a Spanish infectious diseases consultant, is busy in the administration room fielding requests from visitors looking for updates on patients. A man from Unicef calls to see if the lab results are in on a 10-year-old and five-year-old he brought to the hospital the previous night. “Come back at around 5pm,” she advises.

Dr Marta Lado, a volunteer doctor with King’s Sierra Leone Partnership. Photograph: Michael Duff

Running through the whiteboard, she explains that five of the patients belong to one family, including a mother and the newborn baby. Three of her other children, all under 10, were admitted the day before. The outlook for the five is not good. “The mum with four children? They are going to be positive for sure because they have symptoms and have had contact,” says Lado.

Outside, it is chaos. Patients press up against the locked gates to see if they can catch any news through the gaps.

Security guards in wellies mill around a bashed-up maroon car with its doors flung open, seemingly abandoned in the arched entrance beside the isolation unit. A man lies slumped unconscious in the back seat. Nobody pays much heed. An hour later, the car is gone and a corpse lies on a trolley wrapped in a blanket. The man was dead on arrival.

Pooley and colleagues walk briskly through the arch to offices upstairs for an urgent clinicians’ meeting run by his boss, British doctor Oliver Johnson.

A London-born colleague is making an urgent telephone call in the corridor. He is pleading with someone not to admit an Ebola patient to a nearby community hospital in Lumley. An emergency Ebola unit is being built and if the patient is admitted the builders will walk out, he explains. There are only 110 beds in Freetown for Ebola patients and with the disease out of control in the capital, with almost 1,000 cases already confirmed, it is vital the unit’s opening is not delayed.

Like all of those working on the Ebola response in Sierra Leone, Pooley does not dwell too long on the dark side. “In a way, it’s just a job. You know tomorrow will be the same,” he says philosophically. “There is a semblance of normality in Freetown. There’s a huge amount of disruption but people are still getting on with everyday life. This is a wonderful job and it’s got everything I got into nursing for. Arguably the rewards here are greater because the needs are greater.”

He is particularly pleased that two of his patients discharged Ebola-negative were children – a nine-year-old and her seven-month-old sister – but he knows the numbers are not good in Freetown.

“You do feel like things are on the edge of something going horribly wrong when you’ve got people piling up at the entrance and cars coming with corpses in the back and driving off with them before you’ve got a chance to test the corpse or isolate it,” he says.

Everything is chaotic. But he says there is some hope, with a new British hospital in Kerry Town, near Freetown, providing an extra 100 beds.

When he was at home in Suffolk, he had moments of reflection and was “a bit upset at times”. But, he says, this was because he felt so helpless. “It was probably more related to the fact I couldn’t do anything,” he says. “Everyone wants to feel useful.”

Three days later, Pooley is reunited with one of his former patients, Douda Fullah, whose crushingly sad story has been seen by viewers around the world in a video appeal for help. This, he says, is what makes working with Ebola patients worthwhile.

He treated the 24-year-old in a government hospital five hours away in Kenema that bore the brunt of the initial outbreak in Sierra Leone. When he started, the wards had blood and vomit on the floors and walls. Patients had no blankets. Fullah saw five of his family die there before contracting the disease himself. It was not long after that Pooley caught the virus.

They meet on Pooley’s day off, descending into joyous laughter before they embrace as only survivors do in a country running on a “no touch” policy. It is not long before Fullah asks Pooley if he can volunteer at the Connaught, too, just for the day.

“This is a happy day because I am seeing Will,” he says, over and over. Within moments, they are deep in survivors’ banter.

“The first nurse ever to tell me I was Ebola-positive was Will,” says Fullah.

“A dubious distinction,” Pooley laughs. “What did you think when I told you that?”

“I felt very, very bad. I knew I was going to have Ebola because of the kind of direct contact I was having with my father.”

“What did you think your chances were of surviving? “

Will Pooley and Douda Fullah are reunited in seen in Freetown. Photograph: Michael Duff

“Well to me it was high, because I went to the hospital as early as possible.”

Fullah says of Pooley: “I am so, so happy for him. When I heard he was sick, I felt bad. Because there is one thing about Ebola – either you live or you die, so I was thinking of that and I prayed to God for him to get well. I knew it is not the time.”

Pooley teases Fullah: “You couldn’t have been certain otherwise you wouldn’t have needed to pray. There’s a little doubt in your mind maybe.” Fullah explains: “You pray to God for a speedy recovery.”

“I had that, so thank you,” Pooley responds graciously.

They exchange telephone numbers and Pooley talks of rescuing his motorbike in Kenema and realising his original plan to travel around Sierra Leone.

“I don’t want Sierra Leone just to be Ebola in my mind for ever, because it’s such a beautiful place and such nice people. I’d like to just get out there and see it. But that’s a long, long way away.”