Long after contracting COVID-19 in March, UK mother Claire Hastie says she continued to suffer from the aftereffects of the virus.
A former runner, Ms Hastie was fit and healthy before testing positive to the virus. But she says her symptoms got so bad, she sometimes needs to rely on a wheelchair to get around.
Thinking she could not be the only one experiencing this, the single mother of three set up a support group on Facebook for those going through the same experience as her.
"Over time I had a lot of heart pain and palpitations," she said of how she has felt in the months since.
"I got neurological symptoms as well as feeling a real pressure in my head, pronounced pins and needles around by body.
"I have actually been having to use a wheelchair, I used to cycle 13 miles [20 kilometres] a day and now I can't even leave the house."
It wasn't long until word got out about the group, which now has 22,000 members.
Ms Hastie said the group is meant to support COVID-19 survivors who have struggled to get help or recognition that their lingering symptoms existed.
"For lots of months we were completely invisible, so there has been a lot of distress caused by the dismissal and denial," she said.
"Some people have terrible intestinal issues, fatigue, debilitating headaches, loss of sight and some have become incontinent."
Group helps survivors share mysterious symptoms
The support group features a high proportion of fit and active people.
"A lot of people in our group were marathon runners or triathletes, competitive rowers or footballers or even people who aren't even top elite sportspeople but the types of people who would never sit down in an evening," she said.
"It does make me wonder if people who were previously fit are actually more likely to have some sort of immune overreaction or something like that."
Ms Hastie and other members have been using anecdotal evidence to collate their own research.
"It's one of those mysteries that we are so desperate for science and research to catch up with us because we have a hypothesis," she said.
"The science definitely needs to catch up with our experience."
Even mild coronavirus can leave lingering effects
It was a similar coronavirus journey for Amy Durant, who also contracted COVID-19 in March.
The 31-year-old suffered the classic symptoms: a fever, a cough and shortness of breath but was never hospitalised.
Six months on, Ms Durant is still suffering.
"It's just like constant tiredness, it's a weird feeling where as soon as you wake up, I'm just tired and it never really goes away," she told the ABC.
"The chest pain that I had when I was acutely ill has carried over and that hasn't left either."
Amy has dubbed herself a "long hauler" but the term "long COVID" is now being commonly used in the UK, and elsewhere, to describe those suffering from a range of symptoms months after contracting coronavirus.
"It's probably going to become part of the medical language, but it's a term created by patients," respiratory registrarDr David Arnold said.
Dr Arnold is leading a team of researchers at North Bristol NHS Trust to study the symptoms of COVID-19 which linger even after the patient is no longer infectious.
They found three quarters of the 110 patients discharged from Bristol's Southmead hospital in England's southwest after being hospitalised with COVID-19 were still experiencing debilitating symptoms months after first falling ill.
Shortness of breath, muscle aches, significant fatigue, insomnia and chest pain were among ongoing symptoms for patients who have taken part in the study, according to lead researcher Dr David Arnold.
"People are definitely experiencing this," he said.
"We have found it in our research and it's not just us. A study from Italy found 89 per cent of their patients who they looked at six weeks were still experiencing symptoms.
"[Another] study in Austria found around the same. So we are certainly not an outlier."
Immune cells might offer clues for 'long COVID'
Nurse Sue Snelson, 64, ended up in intensive care at the Scunthorpe General Hospital in Lincolnshire in April after contracting the virus.
"I used to manage the unit, so I recognised where I was," she said of the moment she woke after 10 days in the ICU.
After four months off, Sue is now back at the hospital in a limited role after what she described as a "very slow" recovery.
"I still get very short of breath at times, going up a steep slope or upstairs is still difficult and if I talk too much without a break," Ms Snelson said.
"I have actually been told by the consultant that I have a degree of scarring on my lung and I'm always going to have a degree of breathlessness now."
Doctors have not been able to confirm if Ms Snelson has any antibodies for the disease, meaning she must be extra cautious not to contract the virus again.
Due to the scarring on her lungs, she's been told it's unlikely her condition will improve.
"I think people don't realise just how debilitating it is," she said.
"I have grandchildren, you know, and I can't do the things that I did with them before because I get too short of breath."
Dr Arnold said researchers are looking at patients' immune responses and whether a "dampened down" form of the virus is remaining in the body.
"If anywhere, we should be able to find it in a patient's immune cells," he said.
"I would like to say that we will be able to get some answers but I don't think we will be able to tie it all up in a nice bundle."