The novel coronavirus is novel for a few reasons, one of which is, it affects many body systems besides the lungs, and even when sufferers recover, they may see chronic or even lifelong repercussions. "Doctors are now concerned that the pandemic will lead to a significant surge of people battling lasting illnesses and disabilities," said a report in the journal Nature this week. These are some of the sneaky signs you've just had COVID. Read on, and to ensure your health and the health of others, don't miss these Sure Signs You've Already Had Coronavirus.1 Damaged LungsCOVID-19 becomes severe when it moves from the upper respiratory system into the lungs, causing shortness of breath and, in some people, fluid buildup and scarring that can be fatal. Nature reported that although few studies on long-term lung damage have been published, in one study, 88% of hospitalized COVID-19 patients had visible lung damage six weeks after being discharged. The potentially good news is that it may be reversible: By 12 weeks, the number had fallen to 56%. But another study of hospitalized coronavirus patients found that a month after being discharged, more than 70% reported shortness of breath and 13.5% were still using oxygen at home. This seems to parallel previous studies which showed that SARS sufferers experience long-term lung damage.2 Weakened Immune System"Some people who have recovered from COVID-19 could be left with a weakened immune system," reported Nature, which pointed out this has been seen, at least temporarily, with other viruses. Said Daniel Chertow, who studies emerging pathogens at the National Institutes of Health Clinical Center in Bethesda, Maryland: "For a long time, it's been suggested that people who have been infected with measles are immunosuppressed in an extended period and are vulnerable to other infections. I'm not saying that would be the case for COVID, I'm just saying there's a lot we don't know.'"3 Overactive Immune SystemCOVID-10 seems to cause an immune system overreaction in some patients, Nature reports. This can lead to inflammation in a number of organs besides the lungs, including the heart and brain. Effects on the heart are particularly concerning to experts.4 CardiomyopathyOne of those heart effects is cardiomyopathy, in which the heart muscle becomes stiff, thickened, or stretched, says Nature. That affects the heart's ability to pump blood, which can cause anything from fatigue to organ failure.5 Pulmonary Thrombosis"Some patients also have pulmonary thrombosis, in which a clot blocks a blood vessel in the lungs," says Nature. "The virus can also injure the wider circulatory system, for instance, by infecting the cells lining blood vessels." Damage to the lining of blood vessels is the driving force behind heart disease and stroke. Scientists are looking with concern at previous studies that showed people who had pneumonia, a lung disease, experienced higher rates of heart disease up to 10 years later (although they have not yet established a definitive correlation with that outcome and COVID, SARS or MERS).6 Chronic Fatigue"Over the past nine months, an increasing number of people have reported crippling exhaustion and malaise after having the virus," says Nature, pointing up one study of 143 people who had been hospitalized with COVID-19: 53% reported fatigue and 43% had shortness of breath an average of two months after their symptoms started.The long-term nature of this fatigue mirrors chronic fatigue syndrome, a.k.a. myalgic encephalomyelitis (ME), a fact discussed by Dr. Anthony Fauci, the nation's top infectious-disease expert, in several interviews.7 Psychological EffectsIf chronic fatigue becomes a widespread after-effect of COVID-19, "a wave of psychological effects may be imminent," says Nature. Other studies have warned that COVID may affect the brain long term, having chronic effects on the kind and frequency of health care Americans need for decades to come.8 How to Stay HealthyAs for yourself, do everything you can to prevent getting—and spreading—COVID-19 in the first place: Wear your face mask, get tested if you think you have coronavirus, avoid crowds (and bars, and house parties), practice social distancing, only run essential errands, wash your hands regularly, disinfect frequently touched surfaces, and to get through this pandemic at your healthiest, don't miss these 35 Places You're Most Likely to Catch COVID.