“I was very surprised because I hadn’t been very sick at all, and by then I was all better,” Mr King, 54, said.
At about the same time, David Pearson’s cough was developing into something more sinister.
“It felt like my ribs were cracking open,” Mr Pearson, 55, said. “It was almost like I had been in a car crash and had my chest smashed in.”
He was admitted to St Vincent’s Hospital, where he remained for four nights on supplemental oxygen. But he soon rallied.
“I am very much fully recovered,” Mr Pearson said more than a month after being discharged, though he still gets chest pain and recalls one episode of severe headaches.
Both Davids are participants in the ADAPT study led by Associate Professor Gail Matthews, head of infectious diseases at St Vincent’s and Associate Professor at the Kirby Institute, and St Vincent’s respiratory of sleep medicine specialist Dr David Darley.
The study aims to understand why COVID-19 pushes some patients to the brink of death, yet causes no more than a sniffle in others who bounce back quickly.
On Friday, Australia had 7409 confirmed cases, the death toll was 102 and 6877 people had recovered. The latest national COVID-19 surveillance report (dated June 7) showed 1110 cases had been hospitalised, and 205 needed intensive care.
The researchers suspect there is more to this puzzle than age and underlying medical conditions. In Australia, otherwise healthy patients in their 40s were among the critically ill in ICUs.
Internationally, the largest study cohort of more than 44,000 people with COVID-19 from China shows 81 per cent of cases will have mild to moderate symptoms (from a scratchy throat to mild pneumonia). Another 14 per cent will have severe disease and 5 per cent will be critically ill.
Neither David has the faintest idea why the virus affected them as it did.
“It does feel a bit random,” Mr Pearson said. “We thought it was people in poor health and the elderly who got very sick. I may be a little bit overweight but I’m relatively fit and active and only 55, and it really hit me.”
Mr King said: “I’m not the fittest or most active person in the world. I get a cold like everyone else does so I can’t tell you why it didn’t affect me and why it knocks others for six.”
His one curious symptom was a worsening sense of smell after his cough and fever passed.
The researchers have enrolled 50 participants spanning the spectrum of COVID-19 presentations, from those with the mildest of symptoms to patients who were ventilated in intensive care for weeks.
They plan to enrol another 50 patients and monitor their physical health and cognitive function, as well as their psychological well-being for one year from their symptom onset.
The study will also investigate participants’ immune response as they recover: the types of antibodies they develop, how many and for how long they stick around.
“The hypothesis is that most people will develop some form of antibodies but some people will have much higher levels of antibodies than others,” Professor Matthews said.
“If you have a strong antibody response maybe you have more symptoms, and maybe as your antibodies drop off your symptoms resolve.”
COVID-19 is proving to be a disease of the immune system. Triggered by the invading virus, the body’s immune response goes into overdrive, causing acute respiratory failure.
“But what we don’t know is whether this correlates for people who have milder symptoms,” Professor Matthews said.
The mosaic of symptoms include body aches, headaches, joint pain, breathing problems, a tightness or heaviness in their chests, the feeling their heart is racing.
Professor Greg Dore, infectious Diseases Physician at St Vincent’s said the majority of participants – diagnosed in March and early April – are no longer symptomatic, but a significant minority are still reporting symptoms.
“It will be fascinating to see if there is an overactive immune response that may be triggering some of the ongoing symptoms,” Professor Dore said.
The most common complaints are persistent fatigue, Professor Dore said.
In most cases, the feeling of tiredness or exhaustion fades, Professor Dore said, “but an important minority of patients are having symptoms similar to glandular fever and Ross River virus when they report having this prolonged period of profound fatigue”.
As the symptoms drag on, patients worry they may never fully recover.
“It’s not surprising, where you have an illness with a considerable degree of uncertainty, you’ve got people isolating and there’s societal anxiety around COVID in general that some patients will be psychologically impacted.”
“We need to come up with a strategy to address that,” he said. “No symptom should be dismissed.”
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Kate Aubusson is Health Editor of The Sydney Morning Herald.