**2. Materials and Methods**

#### *2.1. Data Collection*

This study was conducted with patients confirmed to have COVID-19, and persons in Daegu and Busan who were isolated (or quarantined) and released from isolation/quarantine during the first wave of the COVID-19 outbreak in South Korea (February– March 2020). Daegu and Busan were the regions in South Korea where the virus spread accelerated during the early stages of the COVID-19 pandemic. As of 31 March 2020, 69.5% of all confirmed cases in the country had occurred in these two regions [24].

In this study, a confirmed case refers to an individual who tested positive on a re-verse transcription-polymerase chain reaction (RT-PCR) test and was treated at a hospital or residential treatment center. A quarantined person refers to an individual who quarantined for two weeks after being ordered to by health authorities, due to close contact or travel abroad, and who tested negative on the final test.

We used an online survey to investigate precautionary behavior practices, for two weeks before COVID-19 confirmation or quarantine, and to investigate COVID-19-related perceptions. The surveyed areas were Daegu and Busan, and all confirmed and quarantined persons who were released from quarantine at the time of the investigation were subject to investigation. However, since Daegu concentrated on the management of confirmed patients as the first outbreak, the management of isolated persons was difficult, so the investigation was excluded. The survey data were collected by sending text messages with a survey link to persons confirmed to have COVID-19, and quarantined persons, in cooperation with Daegu and Busan Infectious Disease Control Centers and public health centers in the regions. Of those, a total of 1716 (1130 patients and 586 quarantined persons) responded to the online survey. By region, in Daegu, the survey link was sent to 5626 patients between 23 April and 20 May 2020, and data were collected from 1100 individuals (19.6%). In Busan, the survey link was sent to 118 patients and 9500 quarantined persons between 28 April and 27 May 2020, and data were collected from 30 (25.4%) and 586 (6.2%) individuals, respectively. The study was approved by the IRB of the Korea National Cancer Center (NCC2020-0104). The data did not contain personally identifying information. All survey participants consented to participate in the study before responding to the survey.

### *2.2. Questionnaire*

#### 2.2.1. COVID-19 Symptoms of Confirmed Patients

COVID-19-confirmed patients were asked what COVID-19 infection-related symptoms they experienced. Specifically, they were instructed to self-report the symptoms they experienced during the period of treatment or quarantine, by selecting from the following list of symptoms: fever, chills, headache, cough, phlegm, muscle aches, sore throat, difficulty breathing, loss of smell, loss of taste, nausea, indigestion, diarrhea, and others.

#### 2.2.2. Precautionary Behavior Practices for Two Weeks before Isolation/Quarantine

The degree to which individuals engaged in precautionary behavior practices for two weeks prior to quarantine or COVID-19 confirmation was assessed using 14 items. Of those, four items concerned handwashing (Q1. I always washed my hands after going to the bathroom; Q2. I always washed my hands (or used hand sanitizer) before eating; Q3. I

washed my hands (or used hand sanitizer) if I thought that my hands might have been contaminated because I shook hands, touched the mask, or held a doorknob; Q4. I washed my hands when I returned home from outside), one concerned cough etiquette (Q1. I covered my mouth with tissue when coughing or coughed into my elbow), four concerned mask-wearing (Q1. I always wore a mask during hospital visit; Q2. I always wore a mask when talking with someone within a two-meter radius; Q3. I wore a mask by ensuring that the mouth and the nose are covered; Q4. I tried to avoid touching the surfaces of used masks), and five concerned person-to-person contact (Q1. I did not attend social gatherings; Q2. My working arrangements has changed (e.g., video or online conferences, working from home, flexible work arrangement, etc.); Q3. I tried to avoid eating out; Q4. I avoided mass gatherings that might bring me into contact with many people; Q5. I avoided contact with others when I had symptoms like fever and a cough). Survey participants self-reported in regard to their precautionary behavior practices, for two weeks before quarantine or COVID-19 confirmation, on a 5-point Likert scale (1 = "not at all" and 5 = "very often"). The item reliability analysis showed that Cronbach's α coefficients were 0.844 for hand washing, 0.866 for mask-wearing, and 0.902 for person-to-person contact (Table 1).



\* Only confirmed patients check all symptoms at onset of infection; n/a: Questionnaires are Not Applicable.

2.2.3. Perceptions of COVID-19 Infection and Psychological States of Persons Who Experienced Isolation/Quarantine

Survey participants' perceptions of COVID-19 infection and their psychological states were assessed through seven items. Of those, three items concerned whether the respondent believed that patients were responsible for the COVID-19 infection (Q1. COVID-19 patients can prevent themselves from contracting the virus; Q2. COVID-19 patients are responsible for their own infection; Q3. It is the COVID-19 patients' own fault that they have the disease) and four concerned fears due to the COVID-19-related situation—two items regarding fear of infection (Q1. I am afraid that I will be re-infected with COVID-19 after receiving treatment; Q2. I am afraid that I will not be fully recovered) and two regarding fear of stigma (Q1. I am afraid of being blamed because I was a confirmed patient infected with COVID-19; Q2. I am afraid that if there are confirmed cases in my area, the area will be criticized or damaged for the reason). The items were all rated on a 5-point Likert scale (1 = "not at all" and 5 = "strongly agree"). The three items regarding the attribution of COVID-19 infection were developed by the researchers in reference to Mak et al. (2006) [25].

To investigate psychological states in the COVID-19 situation, we asked about physical and mental changes (Q1. I am obsessed with searching for COVID-19 news and information; Q2. I am cautious and dubious about other people because I am afraid of getting reinfected; Q3. I feel helpless and am losing interest in what I did well before; Q4. I get more easily annoyed and upset than before; Q5. I have experienced a physical response, such as headache, indigestion, and insomnia) the participants experienced after they were confirmed with COVID-19, or received an order for quarantine, as well as disruption in daily life (Q1. How much did your daily life differ because of the COVID-19 out-break?) due

to COVID-19. The items were developed by the researchers with reference to a guide by the COVID-19 Integrated Mental Health Service Team (2020). Stress due to infectious disease was assessed with five items on a 4-point-Likert scale (1 = "not at all" and 4="strongly agree") [26]. Perceived daily life disruption due to COVID-19 was assessed by using one item on an 11-point scale (0 = "completely stopped" and 10 = "no change") [27].

The item reliability analysis revealed that Cronbach's α coefficients were 0.599 for attribution of COVID-19 infection, 0.704 for fear of infection, 0.759 for fear of stigma, and 0.816 for stress (Table 1).
