"I used to go to the gym three times a week. [Now,] my physical activity is bed to couch, maybe couch to kitchen."

- Athena Akrami, University College London

Science Magazine reports - The list of lingering maladies from COVID-19 is longer and more varied than most doctors could have imagined. Ongoing problems include fatigue, a racing heartbeat, shortness of breath, achy joints, foggy thinking, a persistent loss of sense of smell, and damage to the heart, lungs, kidneys, and brain.

The likelihood of a patient developing persistent symptoms is hard to pin down because different studies track different outcomes and follow survivors for different lengths of time. One group in Italy found that 87% of a patient cohort hospitalized for acute COVID-19 was still struggling 2 months later. Data from the COVID Symptom Study, which uses an app into which millions of people in the United States, United Kingdom, and Sweden have tapped their symptoms, suggest 10% to 15% of people—including some “mild” cases—don’t quickly recover. But with the crisis just months old, no one knows how far into the future symptoms will endure, and whether COVID-19 will prompt the onset of chronic diseases.

SARS2 Covid-19 being discovered only in December 2019 is a virus that had no documented pathology or predictable prognosis. It seeming to be a viral infection with an unpredictable outcome. Some patients are asymptomatic, some endured several weeks of malaise, and others are still enduring its effects weeks or even months after their infections have waned. 
This is why comorbidity, pre-existing conditions, such as hypertension, heart issues, previous cancer treatments are such a significant factor when enduring a Covid-19 infection. 

Covid-19 has caused damage to the lungs, heart, kidneys, circulatory system, brain and neurological system. 
University of Miami Health News has a report here

A Vox report says:

"An estimated 40 to 45 percent of people with Covid-19 may be asymptomatic, and others will have a mild illness with no lasting symptoms. But Nichols is one of many Covid-19 patients who are finding their recovery takes far longer than the two weeks the World Health Organization says people with mild cases can expect. (The WHO says those with severe or critical cases can expect three to six weeks of recovery.)

Because Covid-19 is a new disease, there are no studies about its long-term trajectory for those with more severe symptoms; even the earliest patients to recover in China were only infected a few months ago. But doctors say the novel coronavirus can attach to human cells in many parts of the body and penetrate many major organs, including the heart, kidneys, brain, and even blood vessels.

“The difficulty is sorting out long-term consequences,” says Joseph Brennan, a cardiologist at the Yale School of Medicine. While some patients may fully recover, he and other experts worry others will suffer long-term damage, including lung scarring, heart damage, and neurological and mental health effects."

The National Heart, Lung and Blood Institute of The National Institute of Health reports

"The current scientific literature documenting COVID-19 cases in the U.S. is scattered. But one large report from China, issued in late February, described roughly 44,000 people with confirmed cases of COVID-19. Although most had mild symptoms of the disease, nearly 20 percent were critically ill with lung injury that made breathing difficult. Among the critically ill, many experienced cardiomyopathy and catastrophic arrythmias, prompting a call for more research to study the outcomes and long-term health problems that many patients will face.

The CORAL study is taking charge by looking at two sets of patients: those who were admitted to a hospital and were since discharged, and those who are currently admitted. To learn about eligible participants already discharged from the hospital, researchers will access their electronic medical records for clinical data, chest radiographs, and CT scans. Data and chest imaging on patients currently admitted to the hospital will also be collected so that researchers can document how COVID-19 takes hold of air sacs in both lungs and fills them with fluid—a major hallmark of the disease and the culprit behind the inability to breathe.

To help better understand how COVID-19 impacts more than just the lungs, researchers will also collect information on patient’s cardiac function, and important laboratory tests for markers of inflammation, coagulation, injury to the heart, liver and kidneys, and immunity. Prior reports have documented that patients with poor outcomes, particularly the oldest and most severely ill, were more likely to have abnormal findings in these areas, as well as a higher risk of death."