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Passengers arriving at Incheon International Airport go through point-of-entry screening on May 19. (Yonhap News)

The detection rate for major COVID-19 variants in South Korea stood at 36% last week — up by 13 percentage points from the week before — and has more than tripled in the last month.

Disease control authorities are currently investigating after a patient in Gyeonggi Province tested positive for the Indian variant of the virus in a community infection with no identified transmission route.

One of the patients in a cluster infection involving nightlife establishments in Daegu, with 179 confirmed cases to date, was found to be infected with the UK variant. This suggests that the variant’s previous concentration in Ulsan and its surrounding areas is now spreading into a broader range of regions, including Daegu and Jeju.

On Tuesday, the Central Disease Control Headquarters (CDCH) announced that genetic analysis of virus samples in 723 South Korean patients who tested positive the week before (May 16-22) showed 225 of them to belong to major variants from the UK, South Africa, Brazil or India, giving a variant detection rate of 36.1%.

The rate was 13.6 percentage points higher than the 22.5% recorded for the week of May 9-15, and more than triple the 11% recorded a month early over the period April 20-27.

To monitor the spread of variants, disease control authorities have been randomly selecting samples in proportion to a given region’s population to perform genetic testing.

But the variant detection rate is also being influenced by a rise in testing for regions where variants are spreading.

“As we step up virus monitoring in regions where virus variants are spreading, that increases the number of specimens for that region, which impacts the rise in the detection rate,” CDCH epidemiological research team director Park Young-joon noted in a briefing Tuesday.

Park also said, “The rise in testing in prevalent regions is unavoidable, and it does not pose any major obstacle to our assessing the overall situation.”

The UK variant has been the main driving force behind the rise in the detection rate. Indeed, it accounted for 217 out of 225 domestic cases in which a major variant was confirmed last week.

A total of 100 cases of cluster infections involving virus variants have been detected, and the 17 additional variant cluster infections added last week all involved the UK variant.

The UK variant is also being found throughout South Korea, with clusters involving a church in Seoul — 37 confirmed cases — and an athletic club at a university in Jeju City — 47.

A confirmed case of the UK variant was also identified Tuesday in connection with a cluster infection involving nightlife establishments in Daegu, where 179 people had tested positive as of the start of the day.

“Research has shown the UK variant exhibits a higher permeation rate than non-variants when it enters cells, which makes it as much as 50% more transmissible,” explained Lee Sang-won, director of the CDCH epidemiological analysis team.

“Because of this characteristic, the UK variant is fast becoming the dominant strain throughout the world,” he added. There are no research findings to date that suggest the UK variant is associated with a higher mortality rate.

The South African and Indian variants, which have been reported to evade immunity and partially reduce vaccine effectiveness, were reported in four community cases each.

The four South African variants were not part of a new infection cluster. Instead, they were confirmed through additional genetic analysis of epidemiologically related cases, including a cluster infection involving 108 people at a senior daycare center in Bucheon, Gyeonggi Province.

In the case of the Indian variant, three of the cases were of known provenance, having been diagnosed in connection with a cluster associated with an Incheon International Airport quarantine station.

But the fourth patient, a Gyeonggi man in his 30s, was first identified amid increased monitoring of the local community. Disease control authorities are currently investigating whether clusters involving the Indian variant may already have emerged within the community.

Ten out of 52 patients who arrived from India on special aircraft were also confirmed to have been infected with the Indian variant, but their diagnosis came while they were in quarantine and should have had no impact on domestic cases.

To date, the total number of domestic cases involving variants stands at 3,738, including the 277 added last week. The largest number involved patients in Gyeonggi Province (889), followed by Ulsan (721), South Gyeongsang Province (246) and Seoul (196).

“The vaccines we are currently using have been shown to have some effect against the UK and Indian variants,” Lee Sang-won said.

“We have asked the local governments [in regions where variants are prevalent] to take steps to increase their vaccination rates,” he added.

By Kim Ji-hoon, staff reporter

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