Coronavirus is a multi-organ killer and some survivors may never fully recover as the long-term health effects could be far worse than thought, say doctors and researchers.
Former patients in Italy, including people who suffered a mild infection, have gone on to suffer "chronic damage" with conditions such as psychosis, insomnia, kidney disease, spinal infections, strokes, chronic tiredness and mobility issues.
Separate studies have found that Covid-19 can cause major and permanent damage to the heart and lungs.
Doctors and researchers in Lombardy, one of the worst-hit regions in the world and the epicentre of Italy's outbreak, told Sky News that the virus is a systemic infection that affects all organs and is not, as once thought, just a respiratory disease.
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They say former patients have been unable to do physical activity, return to work or even concentrate while suffering the long-term effects of Covid-19.
All age groups are vulnerable and everyone should take precautions to stay safe, including social distancing, hand washing and the wearing of face coverings, the experts warned.
Dr Roberto Cosentini, head of emergencies at Papa Giovanni XXIII Hospital in Bergamo, told Sky News: "At first, initially, we thought it was a bad flu, then we thought it was a bad flu with a very bad pneumonia, it was the phase when you came here, but subsequently we discovered that it is a systemic illness with vessel damage in the whole body with renal involvement, cerebral involvement.
"So we are seeing other acute manifestations of renal failure that require dialysis; or stroke, and then acute myocardial infarction, so a lot of complications or other manifestations of the virus.
"And also now we see a significant proportion of the population with chronic damage from the virus."
There are fears a devastating second wave could hit Lombardy, where dozens of Britons are thought to have caught the virus on late winter ski trips and brought it home.
Separate studies have found that coronavirus can cause permanent damage to the heart and lungs.
New research by the British Heart Foundation found that 55 per cent of 1,261 patients studied had abnormal changes to the way their heart was pumping, with around one in seven showing evidence of severe dysfunction.
Researchers from University College London had previously identified complications such as delirium, brain inflammation, stroke and nerve damage in patients aged between 16 and 85.
And a new study by King's College London suggests immunity to Covid-19 in recovered patients may only last a few months.
Immunity antibodies decrease significantly in the three months following infection, leaving patients susceptible to reinfection year after year - similar to the common cold, the study found.