Feature MARCO DI LAURO/GETTY MARCO A person who has recovered from COVID-19 takes part in a rehabilitation programme in Genoa, Italy. Gholamrezanezhad says the overall rate of such intermediate-term lung damage is likely to be much lower — his best guess is that it is less than 10%. Nevertheless, given that 28.2 million people are known to have been infected so far, and that the lungs are COVID-19’S just one of the places that clinicians have detected damage, even that low percentage implies that hundreds of thousands of people are experiencing lasting health consequences. Doctors are now concerned that the pandemic will lead to a significant surge LASTING MISERY of people battling lasting illnesses and disabilities. Because the disease is so new, no Months after infection with SARS-CoV-2, some one knows yet what the long-term impacts people are still battling fatigue, lung damage and will be. Some of the damage is likely to be a side effect of intensive treatments such an array of other symptoms. By Michael Marshall as intubation, whereas other lingering problems could be caused by the virus itself. But preliminary studies and existing research into other coronaviruses suggest that the virus he lung scans were the first sign of team started tracking patients in January can injure multiple organs and cause some trouble. In the early weeks of the using computed tomography (CT) scanning surprising symptoms. coronavirus pandemic, clinical to study their lungs. They followed up on People with more severe infections might radiologist Ali Gholamrezanezhad 33 of them more than a month later, and their experience long-term damage not just in their began to notice that some people as-yet-unpublished data suggest that more lungs, but in their heart, immune system, who had cleared their COVID-19 than one-third had tissue death that has led brain and elsewhere. Evidence from previous infection still had distinct signs of to visible scars. The team plans to follow the coronavirus outbreaks, especially the severe damage. “Unfortunately, sometimes group for several years. acute respiratory syndrome (SARS) epidemic, Tthe scar never goes away,” he says. These patients are likely to represent suggests that these effects can last for years. Gholamrezanezhad, at the University of the worst-case scenario. Because most And although in some cases the most Southern California in Los Angeles, and his infected people do not end up in hospital, severe infections also cause the worst Nature | Vol 585 | 17 September 2020 | 339 ©2020 Spri nger Nature Li mited. All rights reserved. Feature Onset of 6 weeks after 12 weeks after COVID-19 discharge discharge G. WIDMANN, C. SCHWABL & A. LUGER/INNSBRUCK MEDICAL UNIV. & A. LUGER/INNSBRUCK C. SCHWABL G. WIDMANN, Lung scans from a 50-year-old show that damage from COVID-19 (red) can improve with time — but many patients have lasting symptoms. long-term impacts, even mild cases can have studies exploring lasting lung damage have immune system. Many other viruses are life-changing effects — notably a lingering been published. Gholamrezanezhad’s team thought to do this. “For a long time, it’s been malaise similar to chronic fatigue syndrome. analysed lung CT images of 919 patients from suggested that people who have been infected Many researchers are now launching published studies1, and found that the lower with measles are immunosuppressed in an follow-up studies of people who had been lobes of the lungs are the most frequently extended period and are vulnerable to other infected with SARS-CoV-2, the virus that causes damaged. The scans were riddled with opaque infections,” says Daniel Chertow, who studies COVID-19. Several of these focus on damage to patches that indicate inflammation, that might emerging pathogens at the National Institutes specific organs or systems; others plan to track make it difficult to breathe during sustained of Health Clinical Center in Bethesda, a range of effects. In the United Kingdom, the exercise. Visible damage normally reduced Maryland. “I’m not saying that would be the Post-Hospitalisation COVID-19 Study (PHOSP- after two weeks1. An Austrian study also found case for COVID, I’m just saying there’s a lot we COVID) aims to follow 10,000 patients for a that lung damage lessened with time: 88% of don’t know.” SARS, for instance, is known to year, analysing clinical factors such as blood participants had visible damage 6 weeks decrease immune-system activity by reducing tests and scans, and collecting data on after being discharged from hospital, but by the production of signalling molecules called biomarkers. A similar study of hundreds of 12 weeks, this number had fallen to 56% (see interferons4. people over 2 years launched in the United go.nature.com/3hiiopi). The virus can also have the opposite States at the end of July. Symptoms might take a long time to fade; a effect, causing parts of the immune system What they find will be crucial in treating study2 posted on the preprint server medRxiv to become overactive and trigger harmful those with lasting symptoms and trying to in August followed up on people who had been inflammation throughout the body. This is prevent new infections from lingering. “We hospitalized, and found that even a month well documented in the acute phase of the need clinical guidelines on what this care after being discharged, more than 70% were illness, and is implicated in some of the short- of survivors of COVID-19 should look like,” reporting shortness of breath and 13.5% were term impacts. For instance, it might explain says Nahid Bhadelia, an infectious-diseases still using oxygen at home. why a small number of children with COVID-19 clinician at Boston University School of Evidence from people infected with other develop widespread inflammation and organ Medicine in Massachusetts, who is setting up a coronaviruses suggests that the damage will problems. clinic to support people with COVID-19. “That linger for some. A study3 published in February This immune over-reaction can also can’t evolve until we quantify the problem.” recorded long-term lung harm from SARS, happen in adults with severe COVID-19, and which is caused by SARS-CoV-1. Between 2003 researchers want to know more about the Enduring effects and 2018, Peixun Zhang at Peking University knock-on effects after the virus has run its In the first few months of the pandemic, as People’s Hospital in Beijing and his colleagues course. “It seems there’s a lag there for it to get governments scrambled to stem the spread tracked the health of 71 people who had been hold of the person and then cause this severe by implementing lockdowns and hospitals hospitalized with SARS. Even after 15 years, inflammation,” says Adrienne Randolph, a struggled to cope with the tide of cases, most 4.6% still had visible lesions on their lungs, and senior associate in critical-care medicine at research focused on treating or preventing 38% had reduced diffusion capacity, meaning Boston Children’s Hospital. “But then the thing infection. that their lungs were poor at transferring is that, long term, when they recover, how long Doctors were well aware that viral oxygen into the blood and removing carbon does it take the immune system to settle back infections could lead to chronic illness, but dioxide from it. to normality?” exploring that was not a priority. “At the COVID-19 often strikes the lungs first, but it beginning, everything was acute, and now is not simply a respiratory disease, and in many Heart of the matter we’re recognizing that there may be more people, the lungs are not the worst-affected An over-reactive immune system can lead to problems,” says Helen Su, an immunologist at organ. In part, that’s because cells in many inflammation, and one particularly susceptible the National Institute of Allergy and Infectious different locations harbour the ACE2 receptor organ is the heart. During the acute phase of Diseases in Bethesda, Maryland. “There is a that is the virus’s major target, but also because COVID-19, about one-third of patients show definite need for long-term studies.” the infection can harm the immune system, cardiovascular symptoms, says Mao Chen, a The obvious place to check for long-term which pervades the whole body. cardiologist at Sichuan University in Chengdu, harm is in the lungs, because COVID-19 begins Some people who have recovered from China. “It’s absolutely one of the short-term as a respiratory infection. Few peer-reviewed COVID-19 could be left with a weakened consequences.” 340 | Nature | Vol 585 | 17 September 2020 ©2020 Spri nger Nature Li mited. All rights reserved. ©2020 Spri nger Nature Li mited. All rights reserved. One such symptom is cardiomyopathy, patients in China showed that 25% had those who ended up on ventilators, says in which the muscles of the heart become abnormal lung function after 3 months, and Chertow. In the worst cases, patients stretched, stiff or thickened, affecting the that 16% were still fatigued8. experience injury to muscles or the nerves heart’s ability to pump blood. Some patients Paul Garner, a infectious-disease researcher that supply them, and often face “a really also have pulmonary thrombosis, in which a at the Liverpool School of Tropical Medicine, long-fought battle on the order of months or clot blocks a blood vessel in the lungs. The UK, has experienced this at first hand. His up to years” to regain their previous health virus can also injure the wider circulatory initial symptoms were mild, but he has since and fitness, he says.