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Background: Patients with coronavirus disease 2019 (COVID-19) can unknowingly spread the virus to several people during the early subclinical period. Methods: We evaluated the viral dynamics in various body fluid specimens, such as nasopharyngeal swab, oropharyngeal swab, saliva, sputum, and urine specimens, of two patients with COVID-19 from hospital day 1 to 9. Additional samples of the saliva were taken at 1 hour, 2 hours, and 4 hours after using a chlorhexidine mouthwash. The severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) viral load was determined by real-time reverse transcriptase polymerase chain reaction (rRT-PCR). Results: SARS-CoV-2 was detected from all the five specimens of both patients by rRT-PCR. The viral load was the highest in the nasopharynx (patient 1 = 8.41 log 10 copies/mL; patient 2 = 7.49 log 10 copies/mL), but it was also remarkably high in the saliva (patient 1 = 6.63 log 10 copies/mL; patient 2 = 7.10 log 10 copies/mL). SARS-CoV-2 was detected up to hospital day 6 (illness day 9 for patient 2) from the saliva of both patients. The viral load in the saliva decreased transiently for 2 hours after using the chlorhexidine mouthwash. Conclusion: SARS-CoV-2 viral load was consistently high in the saliva; it was relatively higher than that in the oropharynx during the early stage of COVID-19. Chlorhexidine mouthwash was effective in reducing the SARS-CoV-2 viral load in the saliva for a short-term period.

Objectives We aimed to compare epidemiologic features of second and third COVID-19 pandemic waves in South Korea. Methods Nationwide COVID-19 data was collected during the study period (May 6–December 30). The degree of social activities was also estimated using the internet searching trend analysis program for leisure-related keywords including “eating-out,” “trip,” and “get directions” (transportation). We compared the demographics, transmission chains, case fatality rates, social activity level, and public health responses between second (August 13–September 18) and third (November 4–present) waves. Results Compared to the second wave, the third wave was characterized by delayed social distancing reinforcement (3 vs. 15 days), longer duration (36 vs. > 56 days) and higher fatality rates (0.91% vs. 1.26%). There was a significant difference in transmission chains of the second and third waves of the COVID-19 pandemic (p < 0.01). During the third wave compared with the second wave, the proportion of local clusters (24.8% vs. 45.7%) was lower, while those of personal contact transmission (38.5% vs. 25.9%) and unknown routes of transmission (23.5% vs. 20.8%) were higher. Conclusion Early and timely interventions with strengthened social distancing policies should be implemented to effectively suppress and control the COVID-19 pandemic.

Doctor's recommendation was the most important factor in encouraging people to be vaccinated against influenza. Doctors should be geared up with precise information and actively encourage high risk population in order to increase vaccination coverage.

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