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People wait in line to get tested for COVID-19 at a temporary screening center in Seoul on Tuesday. (Yonhap News)

As South Korea experiences a full-scale fourth wave of COVID-19 infections, the rate of confirmed patients with the Delta variant of the virus — estimated to be 2.4 times more transmissible — has quintupled in the past week to overtake the rate for those infected with the Alpha variant.

Noting the low rate of Delta variant infections observed last month, the South Korean government said that its “disease control efforts should ultimately have been managed more forcefully.”

The Central Disease Control Headquarters (CDCH) announced Tuesday that genomic testing of 1,071 domestic patients over the week from July 4 to 10 showed 395 of them to be infected with virus variants, giving a detection rate of 36.9%. This means that over three out of every ten confirmed cases domestically involved a variant.

Out of this group, 250 patients were found to be infected with the Delta variant, while 145 had the Alpha variant.

This 23.3% detection rate for the Delta variant was more than double the 9.9% rate (52 patients) calculated the week before. The number of patients with the variant roughly quintupled from 52 to 250. In the greater Seoul area, which has been ground zero for the fourth wave, the detection rate rose by 12.7% to 26.5%.

As recently as the fifth week of June (June 27–July 3), the Alpha variant has the highest domestic variant detection rate at 29%. The latest numbers indicate that the Delta variant had overtaken it just a week later.

“The Delta variant may not yet have become ‘dominant,’ in the sense that it consists for the largest portion of all strains,” said Lee Sang-won, director of the CDCH epidemiological research and analysis group.

“But it’s growing very rapidly, and we can’t rule out the possibility that it will be dominant by around August,” he added.

The swift spread of the Delta variant, which is estimated to be 2.4 times more transmissible than previous strains, prompted the South Korean government to acknowledge that it had been too casual with its judgments through last month.

“As recently as mid-June, the rate of the Delta variant was still quite low, and it was determined that its proportion out of all variants had not reached a worrying level,” said Central Disaster Management Headquarters social strategy group director Son Young-rae on Tuesday.

“Seeing how quickly the Delta variant has been spreading, it could be concluded after the fact that disease control efforts should ultimately have been managed more forcefully,” he said.

To boost variant monitoring, disease control authorities are hurrying to empower local governments to also test for the Delta variant.

“On July 15, we will begin a two-week pilot application of polymerase chain reaction analysis so that Delta variant testing can be performed by local government’s metropolitan and provincial health and environment institutes,” the CDCH said Tuesday.

Under this pilot approach, local governments would selectively make determinations about possible Delta variant infections, after which the Korea Disease Control and Prevention Agency (KDCA) would make a final determination based on whole genome analysis.

The approach appears to have the potential to enable local governments to independently make fast determinations about possible Delta variant cases and perform the necessary tracking and management.

But the central government’s recent unilateral changes to its guidelines — which ease testing and monitoring requirements for arriving international passengers who have been fully vaccinated — have sparked concern among experts.

According to revised guidelines for fully vaccinated South Korean residents that were announced on July 5, testing and monitoring requirements are to be eased for those returning from overseas after being vaccinated in South Korea.

Previously, arriving international passengers have had to undergo at least four separate tests: one within 72 hours prior to arrival, one upon arrival, one on the sixth or seventh day after arrival, and one on the 12th or 13th day after arrival.

In contrast, the amended guidelines reduce the required tests to two: one within 72 hours prior to arrival and another on the sixth or seventh day after arrival.

The monitoring system was also changed from an active one — with the local public health center managing health status on a daily basis — to a more passive approach.

“My understanding is that during a KDCA advisory meeting at the time, they couldn’t reach an agreement because a lot of committee members were opposed to not having that final test on the 12th or 13th day after arrival, but the administration went ahead and unilaterally announced it,” said one infectious disease expert who took part in the guideline amendment process.

Responding to these claims, Lee Sang-won said, “Even people who have been fully vaccinated in South Korea are not exempt from the home quarantine requirement if they are arriving from a country where the Delta variant is prevalent.”

“Based on a working-level examination, some adjustments were made to the testing cycle and methods for those traveling internationally,” he said. “This was meant to establish a system for testing while efficiently allocating limited resources.”

According to the CDCH, a total of 252 suspected “breakthrough” infections had been reported as of Tuesday among the 4,167,322 South Korean residents who have been fully vaccinated.

The rate amounts to 4.46 per 100,000 people, or less than half the 10.2 observed in the US. Two of the patients (0.8%) experienced severe or critical symptoms, while no deaths have been reported.

An analysis conducted on 37 of the patients showed 12 of them to have been infected with variants, including nine cases of the Alpha variant, one of the Beta variant, and two of the Delta variant.

By Seo Hye-mi, staff reporter

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