THE vast majority of those in Ireland and Britain who have tested positive for Covid-19 will be counting their lucky stars that they have had only a mild encounter with the deadly virus – but they may not be able to relax just yet.
There is growing evidence from China, where the virus originated, and from Italy, the first European country to report cases, that patients diagnosed with even a mild case of Covid-19 may be left struggling with long-term health problems long after the virus has left their bodies.
"What we have been seeing in hospitals is the tip of the iceberg," Professor Roberto Pedretti, head of cardiology at the Clinical Scientific Institute in Pavia, Italy, said.
"Our focus at the moment is treating patients at the acute stage to help them recover from Covid-19. But we also need to consider the future health impacts of the virus."
One of these is potential long-term lung damage, which Prof Pedretti fears is going to leave health services worldwide struggling to cope with increasing numbers of Covid-19 survivors who are disabled by reduced lung capacity and require extensive rehabilitation to restore their quality of life.
In severe cases, SARS-CoV-2 (the virus that causes Covid-19 infection) gets deep into the lungs, inflaming the tiny air sacs and filling them with fluid. This prevents the air sacs doing their job of transferring oxygen from the lungs into the bloodstream and taking carbon dioxide out.
This is pneumonia, which in many cases of Covid-19 has been found to affect both lungs. As it progresses, patients struggle to breathe, leading to the potentially fatal condition acute respiratory distress syndrome (ARDS) – where the lungs become severely inflamed.
Many patients affected are unable to breathe unassisted and need to be put on a ventilator.
Even when Covid-19 patients recover from ARDS, they may be left with pulmonary fibrosis – scarring of the lung tissue, which can lead to increasing breathlessness.
Several recent studies have highlighted the growing evidence that Covid-19 causes fibrosis. A research paper published in a Chinese journal in March reported that "extensive" evidence suggests that "pulmonary fibrosis may be one of the major [long-term] complications in Covid-19 patients".
This echoes the findings of a study in Wuhan where researchers analysed the CT scans of 81 patients with Covid-19 and found signs of fibrosis even in those who had had no symptoms, such as a cough or a high temperature (but who had tested positive for the disease).
In the journal Lancet Infectious Diseases in April, researchers said it was unclear if these lung changes were "irreversible".
Not just a risk for hospital patients
Health authorities in Hong Kong revealed in March that among the first dozen patients who had been discharged from hospital after treatment for severe Covid-19, 25 per cent were still suffering from shortness of breath, and "gasping" when walking a bit more quickly.
Despite apparent recovery, "some patients might have a drop of around 20 to 30 per cent in lung function", says Dr Owen Tsang Tak-yin, medical director of the Infectious Disease Centre at Princess Margaret Hospital in Hong Kong.
The UK's Scientific Advisory Group for Emergencies has warned that Covid patients could be left with "extreme tiredness and shortness of breath for several months".
Some experts believe that even those who don't require hospital admission could be affected. The chairman of the Dutch Association of Physicians in Chest Medicine and Tuberculosis warned that thousands of people in the Netherlands who recovered from Covid-19 may be left with permanent lung problems, including people who weren't ill enough to need hospital care.
One theory is that fibrosis occurs as the virus disrupts the wound-healing process. This is what occurred with the SARS coronavirus, the forerunner of Covid-19, according to a paper published in the Journal of Virology in 2017.
Research published in the journal Thorax in 2005 found that six months on, SARS survivors' lung function "was considerably lower than that of a normal population". Part of the problem is the length of time some patients undergo invasive ventilation in intensive care, says Ema Swingwood, chair of the Association of Chartered Physiotherapists in Respiratory Care.
Those on a ventilator need it for "much longer" than normal, she says – "up to 14 days or more". Lengthy exposure to high levels of dehumidified oxygen delivered by ventilation can dry out and damage the mucociliary escalator, the mucus and microscopic 'hairs' that help transport secretions and debris up and out of the airway. Oxygen delivered non-invasively, through masks or nasal tubes, can have the same effect if used for prolonged periods.
Even fit people have been affected
It is not simply that people in poor health before getting Covid-19 suffer worse. "We"re seeing patients we"d never normally expect to see at all who are totally fit and well and have amazing exercise capacity and lung function, and yet they are still suffering lung problems," says Ema.
How much scarring patients develop – and how well the lung recovers – "is very difficult to know at the moment", says Dr Noel Baxter, a GP and a medical adviser to Asthma UK and the British Lung Foundation.
"But there are likely to be some people who end up with some sort of long-term problem".
The British Lung Foundation and Asthma UK have launched the Post-Covid Hub (post-covid.org.uk), a website where patients can be put in direct contact with clinicians.
The advice from the foundation for those affected includes techniques for coping with breathlessness and tips on breaking "unhelpful breathing habits" that can make the problem worse.
Rehabilitation with a tailored programme of exercise for patients who have had Covid-19 will be essential, particularly for patients who have been in intensive care.
But a wider group of people may need help. Karen Middleton, chief executive of the Chartered Society of Physiotherapy, has predicted that "in the coming weeks and months, there will be a tidal wave of rehabilitation need".
Professor Pedretti has begun trials of a potential new rehabilitation treatment for Covid-19 patients unable to exercise enough to restore lung capacity.
The trial will use ReOxy machines, which provide interval hypoxic-hyperoxic treatment (IHHT). This has been used previously to boost fitness in heart patients.
It involves using an alternating mixture of reduced, then either enriched or normal levels of oxygen, administered through a face mask. Intermittently depriving the body of normal levels of oxygen brings about cell changes at a molecular level that make the cardiovascular system more efficient at transporting oxygen.
Research published in the journal High Altitude Medicine & Biology in 2018 found that five weeks of IHHT training was as effective in improving cardiorespiratory fitness in patients as an eight-week conventional exercise programme.
How the virus can harm the heart
Evidence is emerging that in some cases the virus may affect the brain, causing seizures and stroke, as well as harming the liver, kidneys, heart and blood vessels.
A paper in the journal JAMA Cardiology in March reported that one in five of 416 Covid-19 patients hospitalised in Wuhan had suffered heart damage. The researchers also found problems could occur even in those without underlying heart problems.
Another study from Wuhan published in February noted that of 36 patients transferred to intensive care, 16 (44.4 per cent) were suffering from arrhythmia (irregular heartbeats).
The heart problems are thought to occur as a result of the virus triggering a ‘cytokine storm’, where the immune system overreacts to the infection, leading to inflammation of the heart muscle (myocarditis).
As a result, the heart pumps more weakly, causing symptoms such as breathlessness. Myocarditis can also affect the heart’s electrical system, leading to heart rhythm problems.
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