Joe Tannous was a "very fit" and healthy 49-year-old when he was struck down with Covid-19 – and six months on, he still can't walk up the stairs without a struggle.
The lethal virus landed the Australian father-of-three in an induced coma for 10 days – but although he pulled through, he has been in and out of hospital ever since, and everyday tasks are often an impossible challenge.
And he's not alone.
Tannous is one of more than 100 coronavirus patients taking part in groundbreaking research into the pandemic's long-term effects at Sydney's St Vincent's Hospital – and so far, the findings are sobering.
Speaking to 60 Minutes, Professor Greg Dore – one of the study's lead researchers – said many people who only suffered mild virus symptoms were experiencing long-term after effects months after their initial diagnosis.
"Most people are describing ongoing fatigue, reduced exercise tolerance … chest heaviness, some difficulty breathing, and also sort of a brain fog or some issues around attention concentration," Prof Dore told Channel 9.
"People that weren't hospitalised can still have problems breathing. Even for young people infected, the significant post-Covid illnesses we're seeing in should be a bit of a wake up."
Prof Dore said it was "concerning" that many coronavirus patients "didn't get over it".
"The initial acute illness might've resolved somewhat, but then the symptoms continued and, in some respects, did become more constant and more debilitating," he told the programme.
"(They're saying) 'When am I going to get better? When am I going to get back to my life that I had sort of pre-Covid?'"
While many people mistakenly believe coronavirus is only dangerous for the elderly and unhealthy, the research indicates even the young and fit are having their lives turned upside down by the illness.
And many, like Janine Coppi, fear their persistent symptoms will be with them for life.
The 37-year-old former ultra-marathon runner told 60 Minutes she still faced devastating symptoms five months after contracting Covid-19, and that the worst part was the "fear of the unknown".
"Doctors not knowing how to help, what to do, makes it a lot scarier," she said.
Respiratory physician Dr David Darley told reporter Tom Steinfort many patients were experiencing inflammation and even scarring of the lungs many months after falling ill.
"This is bad news. This means that the virus is causing very significant inflammation and pneumonia which can make a patient very sick," he said.