**4. Discussion**

This study was the first to conduct and analyze a follow-up health consultation program provided to patients who recovered from COVID-19 and lived in the region of Korea most severely affected by the outbreak. After the COVID-19 pandemic declaration, social distancing was strictly enforced in Korea, and all individuals with a confirmed infection were quarantined in a single hospitalization room until they recovered fully. Patients were discharged if they showed no physical symptoms and had two or more negative PCR tests. However, despite successful recovery, people reported marked physical and psychological sequelae, meaning that they required further medical advice. Moreover, 28.6% of these individuals required several consultations with doctors. Overall, 27% had physical symptoms; 33% had anxiety; 19.3% had depression; 23.5% had sleep problems, and 53.2% had mental stress. In particular, of the subjects that required two or more consultations, the number of re-confirmed cases was significantly higher among those who were hospitalized in the ICU, those who were symptomatic before hospitalization, or those who complained of physical symptoms after release from quarantine. Furthermore, a higher percentage of those who required multiple consultations reported mild anxiety, mild depression, and mild mental stress than those who required only a single consultation. These results strongly suggested that a follow-up health consultation program delivered by medical professionals and psychologists would play an important role in patient care after release from COVID-19 quarantine.

As mentioned above, patients who recovered from SARS and MERS also reported significant psychological problems after discharge [6,7]. However, the level of psychological distress reported for COVID-19 was much higher, principally because SARS-CoV-2 virus has neurological sequelae through both neuroinvasive and neurovirulent mechanisms. Studies show that SARS-CoV-2 can affect the central nervous system and infiltrate neurons [16]. In addition, unlike SARS or MERS, COVID-19 was declared a pandemic, after which countries implemented strict lockdowns. These lockdowns have had a negative effected on the mental health of the general population, as well as those infected with COVID-19 [17,18]. Also, and most importantly, if a person is infected or has been in close contact with someone who is, he or she has to self-isolate for several weeks. The average period of quarantine in this study was 26 days; patients spent ~4 weeks in an isolated space (hospital room or community treatment center). In particular, psychological distress was severe because patients were allowed no direct contact with others. The mental support provided by professional healthcare providers and psychologists was very important to patients isolated under such conditions. This notion is supported by the results of multivariate analysis, which identified depressive mood and psychological stress as factors that affected the decision to request more consultations.

COVID-19 has a spectrum of clinical symptoms ranging from asymptomatic to severe pneumonia and death [19]. Clinically, the most common symptoms are fever, cough, fatigue, and dyspnea (in that order) [20]. Analysis of 10,237 Korean patients with confirmed COVID-19 revealed that 62% were asymptomatic [21]. Among 40 confirmed patients in a city in Korea, 5% were asymptomatic [22], whereas in an Italian study it was 42.5% [23]. The proportion of asymptomatic patients infected with COVID-19 is thought to be ~40–45% [24]. Among the 1604 subjects examined in this study, 408 (25.4%) were asymptomatic. Common symptoms at diagnosis were cough, fever, myalgia, and dysosmia (in that order), a finding that was somewhat different from that reported in previous studies, probably because the numbers in the study cohorts varied from study to study. In addition, the policies and criteria used for screening tests to identify asymptomatic infections differed from country to country. Moreover, because this study included only those who agreed to participate in the consultation program, there was a possibility that relatively more symptomatic patients joined the program. We thought it interesting that, out of 408 subjects who stated that they were asymptomatic at the time of diagnosis, 29 (7.1%, data not shown) said that they had residual physical symptoms when asked. From March to April 2020, the outbreak in Daegu spread rapidly among a certain religious group [25]. They might not have answered honestly due to a fear of social stigma if they were infected because all their movements and relationships would be exposed [26]. Thus, they might have said they had no symptoms when in fact they did.

In general, according to WHO guidelines, patients can be hospitalized in a ICU if they show severe symptoms, ranging from severe disease to acute respiratory distress syndrome and sepsis [27]. Older age, diabetes, higher body temperature, and lower peripheral oxygen saturation all increase the possibility of ICU hospitalization [28]. Here, we found that subjects diagnosed with COVID-19 based on their symptoms, or those admitted to the ICU owing to the severity of COVID-19 symptoms, experienced more residual symptoms after discharge than those who were asymptomatic. This outcome is plausible because polyneuropathy, myopathy, and reduced pulmonary function are highly likely in patients who have severe disease [29–31]. Therefore, patients with symptomatic or severe COVID-19 infection required a more detailed follow-up program that allows close observation, even after discharge.

We found that 35 patients (2.2%) had re-confirmed COVID-19 after release from quarantine, and this group had the greatest effect on the number of consultations (aOR, 6.703). According to a report by the Korea Centers for Disease Control and Prevention, 292 re-confirmed cases (3.3% of 8922) were reported up until 29 April 2020; these were ascribed not to reactivation or re-infection, but to detection of genetic material from "dead virus" [13]. Similarly, the incidence of re-confirmed COVID-19 RT–PCR results in Italy was 13.7% on Day 14 post-discharge and 14.7% on Day 41 post-discharge [32]. The figure for China was 19% [33]. Here, 12 patients (34.3%) had re-confirmed infection after taking a test on the recommendation of a doctor during the follow-up consultation program because these patients showed residual symptoms that were considered minor but clinically important. Similar results were found in China, where 28% of re-confirmed patients complained of mild symptoms [33]. Re-confirmed cases are much less likely to transmit the disease than those with active infections [13]; however, the viral load is related to the clinical severity of COVID-19 [34], and concerns of infections driven by re-confirmed cases are increasing [14,35,36]. Therefore, physicians must verify whether recovered patients show symptoms; even mild symptoms. Accordingly, a well-structured follow-up program after recovery from COVID-19 (provided by healthcare professionals) will be an effective way to decide whether a patient requires another RT–PCR test.

This study has the following limitations. First, the results cannot be generalized over the general population because it was conducted on an ethnically homogeneous population in a single city. Second, because only patients who agreed to participate in the consultation program were enrolled, there is a possibility of selection bias and overestimation of the results. Third, even though the 20 consulting doctors had the same specialty, they are not professional psychiatrists, so the quality and quantity of consultation may vary. However, a general guideline was provided and a web-based communication site was set up to share information with the consulting doctors to minimize inter-physician variation. Fourth, standardized assessment tools were not applied to evaluate physical and psychological status. Further prospective cohort studies using validated assessment tools are needed.

Despite these limitations, this study has certain strengths. It is the first in which professional healthcare providers implemented a patient management program after discharge; moreover, because Daegu was in the region with the highest number of confirmed cases from February to April 2020, the results could be taken as a reflection of the Korean population during the early COVID-19 pandemic period.
