5. TTX scenario for unexplained respiratory disease outbreak

A family of 4 Korean nationals [father #01 (41 years, male), mother #02 (40 years, female), and son #03 (16 years, male) and his grandfather #04 (66 years, male)] had been on a group tour to Winnan and Hong Kong in China. During the tour, the 4 people were together as a family, and they went mountain hiking in Winnan, then visited a cave, and a local farmer’s market (December 6^th–11^th, 2019), followed by a 3-day tour of Hong Kong (December 11^th–13^th, 2019), before returning to Korea via the Incheon Airport on December 14^th, 2019 (Figure 1). After their return, symptoms began, and Patients #01 and #04 were admitted to a university hospital, where they passed away. The nurses at this hospital, where Patients #01, #02, and #04 were admitted, showed similar symptoms. There were 2 of the 6 individuals returning from the same package tour, had a fever (≥ 38°C) which was detected by thermal screening upon arriving at Incheon Airport.

Travel route of a Korean family who presented with unknown respiratory disease: Outbreak cases. A family of 4 went to Winnan, China where they hiked, visited a cave and a local farmer’s market, then took a 3-day tour of Hong Kong. The return to Korea was via Incheon on December 14^th, 2019.

The clinical symptoms (Table 1) and the travel route of the family are as follows. During the evening before arrival at Incheon Airport, Patient #04 showed symptoms including a dry cough and runny nose. Upon arrival at the Incheon airport, Patients #01 and #02 began to show symptoms of a dry cough, and because no family member had a fever, they passed through the thermal screening at Incheon Airport undetected. The family returned to their home in Seoul in their own car.

Demographics and symptoms of unknown respiratory disease outbreak.

F = female; M = male.

On Day 2 of arrival at dawn, Patient #04 had a fever and chills, whereas Patient #01 went to work in the morning in his own car. Symptoms including an itchy throat, slight cough, and mild fever began. Patient #01 joined a meeting with 10 colleagues at work in the afternoon and had dinner with 3 friends before returning home at 21:00.

On Day 3 of arrival, Patient #04 suffered from aggravated symptoms of a fever (39.4°C), chills, and diarrhea at dawn. Patient #04 was taken to the Emergency Department of a university hospital by Patient #02 around 12:00, and was admitted. Whereas Patient #01 who went to work in his own car in the morning began to suffer from a severe cough, headache, fever (38.3°C), and myalgia, visited an internal medicine clinic close to his company, and was prescribed paracetamol for possible cold symptoms; he left work early. Patient #02, returned home from the Emergency Department after completing the admission process for Patient #04, where symptoms of fever and myalgia began later in the afternoon. Patient #01 took the prescribed paracetamol but still suffered from a fever of 38.5°C, a cough, chills, vomiting, and diarrhea; as Patient #02 showed similar aggravated symptoms of a fever, they visited the Emergency Department and were admitted for suspected acute pneumonia. Patient #03 showed no specific symptoms.

On Day 4 of arrival, Patient #04 showed symptoms of a fever (40.1°C), ophthalmecchymosis, chest pain, dyspnea, and had convulsions at 13:00, followed by the symptoms of epistaxis, hemoptysis, and deterioration of consciousness, which aggravated until his death. At 18:00, Patient #01 showed similar symptoms as Patient #04, which aggravated until his death. At 18:30, Patient #02 was moved to the ICU because of dyspnea. The hospital where Patients #01, #02, and #04 were admitted, ran the tests for suspected diseases including respiratory and waterborne infectious diseases, but the causal pathogen could not be identified; a report was submitted to the KCDC Public Health Emergency Preparedness and Response Center via the 1339 call-line, and simultaneously the public health centers were alerted to the UDO. The request for an epidemiological investigation was made simultaneously to the KCDC, and the city of Seoul. At this time, the media in China and Hong Kong had reported on mortality cases due to an unidentified epidemic.

On Day 5 at 10:20, 3 work colleagues of Patient #01 and 2 of his friends visited the Emergency Department (different regions) and were admitted due to similar symptoms as Patient #01. A nurse at the hospital where Patients #01, #02, and #04 were admitted to, began to show similar symptoms.