Covid "long haulers" suffer ongoing health problems months after the initial infection. Weekend Herald reporter Nicholas Jones talks to a close friend whose life has been turned upside down after he fell sick in March last year.

Luke MacLean-McMahon was 31 and in the shape of his life before being hit by Covid-19.

Nearly 19 months later he can't do the sports and exercise he used to love, after the disease damaged his heart and caused a host of other health problems.

He'd dismissed the early media reports of a virus spreading from China as overly hyped. Besides, the advice was that for most people it would be a mild illness.

The elderly were at most risk, and he reassured his Porirua-based grandparents when farewelling them after a trip home from Britain over Christmas.

"I told them not to worry," he remembers. "I thought it was just a beat-up."

Back in London, that media coverage intensified. A friend suggested they stock up on supplies like Panadol, just in case. The shelves of a multi-storey chemist at Piccadilly Circus were stripped bare. It was the same story at a supermarket on the way home.

That night, Friday March 13, he woke with body aches like he'd never experienced - "like I was being bashed all over" - and stayed in bed the entire weekend, with no energy, no appetite and increasing headaches.

He felt a bit better at times throughout the week, but by the following Saturday fever had set in. Shivering in sweat-soaked sheets he could barely sit up, he says.

"I had lost all strength. I remember rolling out of the bed and dragging myself across the hallway to the bathroom. Fluctuating between really hot and freezing cold. I turned the shower on and lay on the floor under the hot water because I was so cold. Then back to bed for a few days."

Luke was house-sitting alone, for close friends in West Hampstead. By this point London was in lockdown, so nobody could check on him.

"I was boiling the jug and putting Vicks in a bowl and trying to steam my lungs, with a towel over my head. And lying on the floor googling how to breathe, because I couldn't breathe normally. I was gasping for air.

"I had lost my voice, and kept calling the UK healthline to try to get medical advice. I called the ambulance twice but I wasn't loud enough when I finally got through."

The city seemed silent except for sirens. Blue and red lights flashed on to the brick of the flats across from his bedroom window. He saw two neighbours loaded into ambulances.

Health services were in overload but a friend eventually managed to order him an ambulance, which took about eight hours to arrive. She'd told him to pack a bag and be ready by the front door downstairs.

"I slid down the stairs. I was as sick as I had ever been. I fell asleep and woke up to them bashing the door. I remember the oxygen going on me ... they didn't have PPE, they had ripped up rubbish bags across them."

At the Royal Free Hospital, north of Camden Town, "everyone was heaving - really intense coughing," he remembers. He wasn't in good shape but after a few days was discharged after a nurse explained they needed the bed for people in even worse condition. "The people who helped me are heroes," Luke says. "It was obvious they were busy trying to save others who were in worse situations."

In the following weeks, doctors prescribed different steroids to try to reduce inflammation of his lungs. He didn't feel much better - his heart would race out of control, he had chest pains and palpitations, and the same intense fever came and went.

He was in and out of hospital, and dropped from 88kg to 76kg in three weeks because of the loss of an appetite that normally demanded two or three portions.

Most visits included receiving oxygen and heart tests and checks. It was explained if his deterioration continued that he'd be put on a ventilator, a machine that takes over the body's breathing process.

"The nurse held my hand and suggested I contact my family. That was probably the hardest moment."

He wrote a letter to his 2-year-old niece, who was thousands of miles away with his sister and parents at home in Rarotonga. "A letter about how amazing life, the world and travelling is. Not to let Covid change that and go out and try to do everything she can."

Thankfully his vitals improved, but in the following months he struggled with debilitating problems including heart palpitations, fevers, severe chronic fatigue and stomach issues. For three or four days at a time he'd suffer from vertigo and frequently throw up.

The country remained in lockdown. His friends Zoe and Matty cycled across London to drop food off at his door, an act of friendship he's forever grateful for.

About four months after he first got sick his doctor and physiotherapist suggested he could finally try a walk around the block, but he woke up in hospital after blacking out.

Luke decided to return to Rarotonga to see his family when a nurse he'd become friends with told him their rostering was preparing for a second Covid wave.

After collapsing in his MIQ room at the Stamford Plaza he was taken to Auckland City Hospital for checks. It was only then that his heart problems were finally found, he says, including a severely enlarged left ventricle, irregular heartbeat and damaged tissue.

"They call it Covid scarring of the heart. I had asthma as a kid but there was no other underlying health and heart condition before that. There has been permanent damage or scarring."

After four months in Rarotonga, where symptoms continued including blackouts and vertigo, he returned to Auckland in January for further tests. Since then he's had about 50 medical visits, including for brain, lung and heart scans, and to fit heart monitors.

So far, Luke has been diagnosed with long Covid, dysautonomia (problems with the autonomic nervous system) and PTSD.

Most people with Covid-19 recover completely, but some people report a wide range of symptoms beyond the time of "recovery" from the acute phase of the illness. These can last for weeks or months, vary from mild to severe, and come and go. They commonly include fatigue, shortness of breath, headaches, "brain fog" and anxiety.

Ongoing symptoms are common after many viral and bacterial infections, but because SARS-CoV-2 was discovered in 2019 there's still limited knowledge about long Covid, although research is rapidly expanding.

Long Covid is likely not a single condition, and appears to be more common among older people and those who got very sick initially. However, it can also develop in those who only had mild or moderate illness, and in younger people (including children) with no pre-existing conditions.

Estimating how many people are affected is difficult because studies have used different measurement and inclusion criteria, but larger studies are under way and the World Health Organisation this week released a clinical case definition.

Last week the director general of health, Dr Ashley Bloomfield, cited a new study, by the University of Oxford and Britain's National Institute for Health Research, that included more than 270,000 people and found 37 per cent of patients had at least one long-Covid symptom, diagnosed three to six months after infection.

"To be clear, long Covid is real," Bloomfield said at the 1pm press conference. "Although people who get flu or other viral illnesses can also have prolonged post-viral symptoms, this study found the symptoms linked to Covid were 50 per cent more common in those who had Covid compared to people who had had flu."

Luke's medical team includes Dr Pete Storey, a clinical immunologist, allergist and general physician and one of the consultants who has looked after Auckland City Hospital's Covid inpatients since the start of the pandemic, including after discharge.

"People think of Covid as a virus, but actually the reason why an immunologist looks after Covid patients is because, yes, the virus infection is the trigger, but all of the problems such as inflammation of heart muscle, inflammation in the lungs that causes breathing problems, they are all the immune response," he says.

Early in the pandemic, treatment and hospitalisations focused on people's breathing problems, Storey says, but more evidence had since emerged of how inflammatory problems might be causing complications like heart inflammation and injury to the heart muscle.

Heart inflammation (myocarditis and pericarditis) is an extremely rare side effect of mRNA Covid-19 vaccines (including Pfizer), and was linked to the death of a New Zealand woman in August. However, such inflammation is much more likely to happen and be more severe after catching Covid, and experts stress the benefits of vaccination far outweigh the risks.

Professor Jason Kovacic, executive director of Sydney's Victor Chang Cardiac Research Institute, has recently said that, while evidence of prevalence is still emerging, the Delta variant appeared to put young, healthy people at more risk of serious heart complications, including myocarditis.

"Anecdotally we're certainly seeing a few more cases of cardiac complications in younger people from Delta," he told the ABC last month. "These complications involving the heart are a very significant problem, but thankfully, it's still the minority of people with that experience."

Luke has been told another explanation for some of his ongoing symptoms may be dysautonomia, which is a dysfunction in the part of the nervous system that works automatically to regulate bodily functions, including heart rate and blood pressure.

"If you are sitting down and then stand up, your blood pressure needs are different, depending on what position you are in. But you don't consciously think, 'I need to increase my blood pressure'. Signals within the body itself will tell your body to increase the blood pressure in a number of ways," explains Storey.

"If those signals are damaged in some way you can see that wouldn't work as well and it wouldn't be as responsive. And so then you could see problems like irregular heartbeat or blood-pressure problems that could cause you to black out. Although we haven't really got our finger on what exactly happens in long Covid, it seems to be that there is some damage to that signalling, and that's why things fall out of kilter."

Long Covid is a "catch-all" name for what is likely to be a range of conditions and causes, Storey says. Some might be because of an ongoing immune response, others because of damage from inflammation in the initial stages of infection.

"Maybe when we understand more ... we will have different [diagnostic] names for different people. We are trying to study in more detail what could be happening in the immune system, and is there a blood test that could detect this? What does that tell us about what the condition is? But there's no question it is a nasty disease."

Being sick with a condition that's not yet well understood adds to the burden for Covid "long haulers". They can be given competing views by specialists, or not have their symptoms taken seriously by medical professionals, and friends and family. There's no certainty around recovery prospects. A more minor issue: Luke's had 39 nasal swab tests for Covid, and counting.

Luke, who is Cook Island Māori, grappled with going public with his story, but has decided to do so to encourage others to get vaccinated, particularly young Māori and Pacific New Zealanders. He's working with Māori and Pacific health providers in Porirua to share his story and has joined Zoom calls with community and health groups.

He was the life of the party before his illness - the sort of friend who is the glue in a wider circle, organising event tickets or weekends away, the last to bed after too many beers but first up for bush walks and other activities, yet somehow finding the energy for a game of tennis or basketball.

Now, he avoids alcohol and certain foods because they can exacerbate his symptoms, as well as any exercise that stresses his heart too much. He is slowly testing his body with daily walks and - before lockdown - gym rehabilitation, helped by a trainer and friends Vin, Alex and Nick. He can now feel his blackouts coming on, and get on to the ground.

The new limits have been hard to accept; a few months ago he risked a game of basketball with his old team, but had heart palpitations, blackouts and vertigo for days afterwards. The same thing happened when he joined his dad for an outrigger canoe outing when home in Rarotonga.

"It was something that I wanted to do together with Dad. You are out in the ocean looking back at the island. I went out and it was epic. But I was cooked for four days afterwards, bedridden.

"I am determined to get through at least a set of tennis soon. Small things like that. Before getting Covid I thought about running a marathon. Now it's a dream of mine that maybe I'll walk a half marathon one day."

The ordeal has been "agony" for his family, his mum Anne McMahon says. Closed borders meant they couldn't fly from Rarotonga to his side in Britain, including during "some touch and go moments".

"We felt absolutely helpless and are forever thankful to those health workers and good friends in London that looked after and cared for our son.

"As a parent you always want and do all that you can to take away a child's pain, worry, fear and doubt about anything and everything. Covid is proving tough. We can't do anything to help Luke with the physical toll of Covid but we have as a family stretched ourselves enormously to help him with the emotional and mental impact of Covid. We will continue to do that.

"We believe that his physical and mental fitness is probably a major factor as to why he is with us."

The more infectious and dangerous Delta variant is now circulating in the North Island, as restrictions ease in Auckland.

Health workers are braced for a big surge in cases. That would affect everyone because non-Covid treatment and surgeries will be cancelled as staff are redeployed. Hospital contingency plans for a "red alert" uncontrolled outbreak, obtained by the Herald under the Official Information Act, show doctors could face "ethical decisions on which patients to treat".

Infections can occur in those who are vaccinated, and there are cases where those people suffer long Covid. However, Luke's specialist, Dr Pete Storey, says breakthrough infections are unusual, and he has seen first-hand how it is the unvaccinated who end up in hospital. (The Ministry of Health says vaccination helps reduce transmission, and the effectiveness of two doses of the Pfizer vaccine against symptomatic illness is 64-95 per cent, and against hospitalisation or severe disease is about 90-96 per cent).

"Early on in the pandemic we thought Covid would affect older people more, people with other medical problems more. But certainly with the Delta variant, it is young, fit, healthy people that are needing increasing amounts of hospital care. Covid doesn't discriminate. It is not worth the risk," Storey says.

"There is still a lot about suffering with Covid that we don't understand. And the old adage that prevention is better than cure is absolutely true for this. You just want to do all you can to prevent getting Covid. And what can you do for that? Get vaccinated."

Currently, Māori and Pacific vaccination rates are lagging well behind Pākehā and for Asian people, particularly in the younger age brackets.

That worries Luke, who says if his story convinces even a few dozen Kiwis to get protected it will be worth the loss of privacy.

"People often ask if the vaccines were available before I got sick would I have got vaccinated then? Absolutely. I urge everyone to get vaccinated. And encourage those you know to do the same.

"I used to think I was reasonably young, fit and healthy. I was usually pretty active doing something every day. Basketball. Tennis. Those are the things I love and I can't do that anymore.

"It's a hard thing to realise. I'm still grieving losing those things."