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People wait in line to get tested for COVID-19 at a temporary screening center in Jeju that suffered wind damage as Typhoon Omais approached South Korea on Monday. (Yonhap News)

The amount of viral particles released by patients infected with the Delta variant of the COVID-19 virus on the day their symptoms first appear is up to 300 times larger than in patients infected with previous variants, a study shows.

The finding shows that the Delta variant has a higher level of transmissibility in the early stages of symptom manifestation. The detection rate for the Delta variant among domestic confirmed patients in South Korea stood at 89.6% at last count, up by 4.3 percentage points from the week before.

The findings were included in an announcement Tuesday by the Central Disease Control Headquarters (CDCH) on the current situation with viral variants in South Korea.

To examine initial transmissibility in domestic patients infected with the Delta variant, the CDCH recently performed a comparative analysis of 1,848 respiratory samples from Delta variant patients and 22,106 samples from patients with other variants on the days after their symptoms appeared.

The samples from Delta patients showed the virus detected at levels around 300 or more times higher than in the samples from other patients on the day that symptoms first manifested. This rate dropped to 30 times higher by the fourth day after symptoms appeared and 10 or more times higher by the ninth day; after 10 days, the difference disappeared.

This suggests that the Delta variant is far more transmissible in the earliest stages after symptoms appear.

An analysis of 26.2% of domestic confirmed cases over the past week showed 90.4% of the patients to be infected with major variants, a rise of 3.5 percentage points compared with the 86.9% recorded the week before.

The Delta variant detection rate stood at 89.6%, up by 4.3 percentage points from 85.3% the week before. This means that nearly nine out of ten new confirmed cases in the community are patients infected with the Delta variant.

“With the Delta variant currently spreading, it is more important than ever that people with possible COVID-19 symptoms immediately get tested, that they avoid contact and gatherings with others, and that they observe basic disease prevention rules such as always wearing masks in order to prevent transmission,” the CDCH said.

By Kim Ji-hoon, staff reporter

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