NPIs diminished SARS-CoV-2 transmission in South Korea
In South Korea, the first cases of severe infection with the coronavirus 2 (SARS-CoV-2) with acute respiratory syndrome were detected in January 2020. By April 2020, the number of cases with coronavirus (COVID-19) rose to 10,683 infections, 237 people had died from the disease.
A large percentage of the cases and deaths were the result of superspreader events in Daegu-Gyeongsangbuk Province. At the beginning of the outbreak, health officials raised the infectious disease alert to 3, the highest in South Korea. Increased screenings and tests were then carried out by drive-through screening centers and COVID-19 testing facilities in private hospitals. In April 2020, the social distancing measures implemented in March were relaxed as the COVID-19 epidemic in South Korea was under control.
Although some studies have looked at how public health interventions can help contain COVID-19 outbreaks, not much information on public health measures against the transmission of SARS-CoV-2 was available, particularly in South Korea.
Analysis of COVID-19 transmission outside Daegu-Gyeongsangbuk Province
Researchers from Konyang University College of Medicine in South Korea and the University of Hong Kong in Hong Kong analyzed the transmission of COVID-19 outside of South Korea’s Daegu-Gyeongsangbuk provincial region in a study recently published in the CDC’s Emerging Journal of Infectious Diseases.
The team estimated the transmittability of the SARS-CoV-2 virus and determined the impact of public health interventions outside of Daegu-Gyeongsangbuk Province in South Korea. The researchers collected local health data from the city or province public health departments. The data collected included the source of infection, the date of exposure and the onset of disease, as well as the contact history and the age and gender of the patients. Your analysis was limited to regions in South Korea outside of the Daegu-Gyeongsangbuk provincial region. During the three-month study period (January 20 to April 21, 2020), data was collected for 2,023 cases, covering approximately 98% of the 2,066 cases reported by the South Korean Ministry of Health and Social Affairs.
They analyzed the time between onset of illness and laboratory confirmation for 818 symptomatic case patients. Data for 181 patients whose precise history of contact with other confirmed cases was known were analyzed to estimate the incubation period. They identified 44 infection clusters and 79 case patients who were exposed to only one index case patient among the clusters.
To determine the effectiveness of non-pharmaceutical interventions in South Korea, the team estimated a real-time measure of transmission intensity, instantaneous effective reproductive number (Rt) from the daily occurrence of cases, and their estimated serial interval distribution. Daily RT estimates were submitted from February 16, 2020 as stable RT estimates were not available due to the small number of confirmed cases.
Non-pharmaceutical measures reduced transmission without blocking
A combination of non-pharmaceutical interventions such as improved screening, quarantining of suspected and confirmed cases, and social distancing measures have been enforced in South Korea over time. The results of the study suggest that even without lockdown, these interventions have helped reduce the transferability of SARS-CoV-2 outside the Daegu-Gyeongsangbuk provincial region.
The results suggest that non-pharmaceutical interventions used in South Korea during the early stages of the COVID-19 outbreak reduced virus transmissibility and included the spread of the virus in the local community. They estimated that non-pharmaceutical measures reduced transmission by around 34% without imposing a strict lockdown in the province. They also noted that optimizing disease control requires continued efforts to monitor the transferability of COVID19. However, the researchers warn that South Korea may continue to be vulnerable to further epidemic waves or outbreaks.
As the infection can continue to be imported by travelers from overseas, ongoing monitoring of reproductive numbers is required to collect relevant data that will help policymakers implement measures to combat a potential second wave of COVID-19 in South Korea.
“Our results suggest that these non-lockdown interventions reduced the transferability of SARS-CoV-2 in regions outside of the Daegu-Gyeongsangbuk provincial region of South Korea.”
Limits of the Study
The study also has some limitations. Large clusters reported as super spreaders were not included in the analysis of changes in SARS-CoV-2 transferability. There may also be undetected cases that were not part of the study, which could mislead the actual trends of infections in the specific population. The estimates in the study were based on self-reported data, which tend to report bias. In the absence of government-generated data, they used data from online case reports, which may have resulted in inaccuracies in the information used in the analyzes.