Sunghee Park,^1,a So Yun Lim,^1,a Ji Yeun Kim,^1,a Heedo Park,^2,3,a Joon Seo Lim,⁴ Seongman Bae,¹ Jeonghun Kim,^2,3 Jiwon Jung,¹ Min Jae Kim,¹ Yong Pil Chong,¹ Sang-Ho Choi,¹ Sang-Oh Lee,¹ Yang Soo Kim,¹ Man-Seong Park,^2,3,b and Sung-Han Kim^1,b

¹Department of Infectious Diseases, Asan Medical Center, University of Ulsan College of Medicine, Seoul, South Korea; ²BK21 Graduate Program, Department of Biomedical Sciences, Korea University College of Medicine, Seoul, Republic of Korea; ³Department of Microbiology, Institute for Viral Diseases, Biosafety Center, College of Medicine, Korea University, Seoul, South Korea; and ⁴Clinical Research Center, Asan Institute for Life Sciences, Asan Medical Center, University of Ulsan College of Medicine, Seoul, South Korea

^aS. P., S. Y. L., J. Y. K., and J. H. P. contributed equally to this work.
^bM.-S. P. and S.-H. K. contributed equally to this work as senior authors.

Correspondence: S.-H. Kim

Background
Data on the clinical and virological characteristics of the Delta variant of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) are limited. This prospective cohort study compared the characteristics of the Delta variant to other variants.

Methods
Adult patients with mild coronavirus disease 2019 (COVID-19) who agreed to daily saliva sampling at a community isolation facility in South Korea between July and August 2021 were enrolled. Scores of 28 COVID-19-related symptoms were recorded daily. The genomic RNA and subgenomic RNA from saliva samples were measured by real-time reverse-transcription polymerase chain reaction (PCR). Cell cultures were performed on saliva samples with positive genomic RNA results.

Results
A total of 141 patients (Delta group, n = 108 [77%]; non-Delta group, n = 33 [23%]) were enrolled. Myalgia was more common in the Delta group than in the non-Delta group (52% vs 27%, P = .03). Total symptom scores were significantly higher in the Delta group between days 3 and 10 after symptom onset. Initial genomic RNA titers were similar between the 2 groups; however, during the late course of disease, genomic RNA titers were higher in the Delta group. Negative conversion of subgenomic RNA was slower in the Delta group (median 9 vs 5 days; P < .001). The duration of viral shedding in terms of positive viral culture was also longer in the Delta group (median 5 vs 3 days; P = .002).

Conclusions
COVID-19 patients infected with the Delta variant exhibited prolonged viable viral shedding with more severe symptoms than those infected with non-Delta variants.