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The death toll from the coronavirus pandemic has climbed further above the grim milestone of one million.
Yet doctors are still trying to understand more about how the virus attacks the body.
Breathing difficulties and shortness of breath are unsurprising after-effects of the respiratory illness.
But medics are finding that Covid-19 is causing cardiac, renal, neurological, abdominal and even blood-clotting problems.
The extreme lethargy and tiredness that some have reported is also a possible consequence of poorly performing lungs, according to Dr Bharat Pankhania, a senior clinical lecturer at the University of Exeter in the UK and consultant in communicable disease control.
Dr Pankhania said a symptom in a minority of Covid-19 patients, excessive blood clotting, was harder to explain.
“We’re picking up unusual features such as cardiac problems, renal problems, neurological problems, abdominal problems, blood-clotting problems,” he said.
“It’s a wide range of signs and symptoms. It’s pretty unusual to have such extensive signs and symptoms. It really is unusual.”
This view is echoed by an online briefing document from the Penn Medicine healthcare system in the United States, which said that, as well as symptoms such as fever, fatigue and breathlessness, post-Covid effects could include impaired kidney and cardiovascular function, ongoing blood-clotting issues, muscle pain and depression.
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A UK Parliament briefing document highlighted additional persistent symptoms such as chest pain, joint pain and difficulties concentrating or focusing on immediate tasks.
"There is growing evidence from follow-up of patients that the SARS-CoV-2 virus which causes Covid-19 is not restricted in its influence on the pulmonary system but causes a long-lasting impact on multiple systems of the individual," a report in The Physician stated.
One possible explanation for the wide-ranging effects centres on the ACE2 receptor, a protein found on the surface of many types of cell in the body.
It is by binding to this receptor that the coronavirus, which is officially known as SARS-CoV-2, gains entry and infects cells.
“You can argue that so many organs are affected because the human body has extensive ACE2 receptors in various organs – the heart and lungs and kidneys all have ACE2 receptors – and that’s the receptor by which this virus exerts its effects,” said Dr Pankhania.
“Once you’re infected, it has this welcome [receptor] in many parts of the body.”
Among those suffering from persistent effects of a coronavirus infection, Dr Pankhania said some were likely to find that their symptoms improved after months, but it was possible a proportion would experience lingering effects for even years.
“I’ve a feeling there’s going to be a post-viral fatigue syndrome and there are some unusual pathologies that we never even expected,” he said.
