[Q&A] "Possible Infection Two Days Before COVID-19 Outbreak... Expanding Epidemiological Investigation Scope"

On the 3rd, a fence with the phrase "Together, we can overcome if we block it" was placed at the COVID-19 screening clinic exclusively for overseas arrivals, set up at the West Gate 1 parking lot of Jamsil Sports Complex in Songpa-gu, Seoul. Photo by Moon Honam munonam@

[Asia Economy Reporter Choi Dae-yeol] On the 3rd, quarantine authorities announced that when investigating contacts or movement paths of confirmed patients with the novel coronavirus infection (COVID-19), they are now investigating from two days before symptoms appear. Previously, the standard was one day before onset, but this change is based on the judgment that virus transmission to surrounding people is possible even when there are no early symptoms of infection.

Jung Eun-kyung, head of the Central Disaster and Safety Countermeasure Headquarters for COVID-19, said at a briefing on the 3rd, "Since there was a possibility raised that transmission is possible even during the asymptomatic period before onset, when investigating contacts, we are considering the two days before onset as the infectious period and conducting investigations accordingly."

Currently, using one day before onset as the standard was a measure reflecting the typical characteristics of respiratory infectious viruses. Generally, even if exposed to the virus and infected, it was judged that symptoms must appear to the extent that the virus can spread to others. However, in the case of COVID-19, it has been known that transmission easily occurs from the early stage of infection, so contacts and movement paths have been investigated from one day before onset. This standard has now been moved one day earlier. It is expected that the disclosure of confirmed patients' movement paths by local governments will also change to start from two days before onset.

The following is a Q&A with Head Jung Eun-kyung at the briefing that day.

- When is the first patient identified in the cluster infection at Uijeongbu St. Mary's Hospital?

▲ So far, there are a total of 27 confirmed cases. In the six wards where patients occurred, follow-up investigations are being conducted on discharged patients, their caregivers, and related personnel. Besides the initially confirmed 75-year-old patient, about four patients with earlier onset dates have been identified. Two of them are being investigated through medical records as their symptoms are judged to be due to diseases other than COVID-19, and the other two are under investigation. The onset dates appear to be around the 22nd of last month, and we are examining whether the symptoms are due to COVID-19 or underlying diseases.

- Since cluster infections at public bathhouses have been confirmed, is there a need to refrain from using them?

▲ If there are symptomatic patients, all spaces where close contact occurs can be places of transmission. It is difficult to say all spaces are risky, but close contact within 1 meter in enclosed spaces can transmit the virus. If symptoms are present, we urge people to stay home and avoid going out, emphasizing physical distancing. The cluster infections at bathhouses are considered to have occurred because acquaintances met there and had close conversations. There is no space that is safe or unsafe per se.

- Overseas crew members are not subject to mandatory two-week self-quarantine; is this being reconsidered?

▲ Crew members follow infection prevention guidelines provided by airlines or the Ministry of Land, Infrastructure and Transport, and their symptoms such as fever are checked twice daily. When staying abroad, they stay in hotels and do not go out. If classified as symptomatic or contacts of patients, they undergo testing and other measures along with other suspected cases. If all arrivals from overseas were subjected to mandatory two-week self-quarantine, flight schedules would be difficult to maintain.

- What were the diagnostic test results of the internal medicine doctor who died in Daegu?

▲ It is believed that the doctor was infected through exposure while treating patients before being confirmed positive. The cause of death will be reviewed through the Central Clinical Committee after examining medical records. The attending physician classified the death as related to pneumonia caused by COVID-19. During pneumonia treatment, the patient also received treatment for myocardial infarction. Detailed underlying conditions will not be disclosed.

- What is your view on the necessity of using rapid diagnostic tools in parallel?

▲ In the U.S., one antibody diagnostic kit has been approved. Currently, the RT-PCR we use is a gene amplification test used for confirmation. Diagnostic kits utilizing antigens and antibodies are considered necessary. However, it takes some time after infection for antibodies to form. More research is needed on how quickly antibodies form and how long they last. Antibodies form at least 5 to 12 days after infection, so antibody testing has limitations for early infection diagnosis. In Korea, diagnosis is made about two days after onset and many asymptomatic cases are diagnosed, so antibody testing has limitations. After some time, antibody testing is considered necessary as an auxiliary method. We are developing testing methods and conducting antibody tests on some confirmed patients. Diagnostic kits will be reviewed upon application in consultation with the Ministry of Food and Drug Safety.

- Are the 10 confirmed staff members related to Uijeongbu St. Mary's Hospital medical personnel? How is the first source of infection being identified?

▲ There are 2 nurses, 6 caregivers, and 2 general staff. The cause of infection within the hospital is under investigation. Including pediatric patients at Asan Hospital, infection routes are being investigated, but it is still early to clarify the cause. We have secured the list of discharged patients and their guardians who were admitted to the wards where confirmed cases occurred after the 17th of last month. One patient transferred to Myongji Hospital was confirmed through screening.

- Is epidemiological investigation still ongoing for cluster infections such as Shincheonji where the first source of infection has not been identified?

▲ For large-scale outbreaks, investigations on infection sources and routes are ongoing. A pan-government epidemiological investigation support team has been formed, and investigations are underway using various big data such as immigration information and records obtained from Shincheonji. Although infection routes and first sources are being investigated, priority is given to quickly identifying contacts and taking measures for group facilities, while infection route investigations will be conducted over time.