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

Disease control authorities have officially announced South Korea’s “fourth wave” of COVID-19 infections underway, with over 1,200 confirmed cases recorded Tuesday.

But many predict the spread could end up even more intense than all three previous waves as younger people in the greater Seoul area are impacted by the virus’ highly transmissible Alpha and Delta variants.

The Central Disease Control Headquarters (CDCH) announced Wednesday that a total of 1,212 new confirmed cases had been counted by the end of the day Tuesday, including 990 in the greater Seoul area (Seoul, Incheon, and Gyeonggi Province), or 84.8% of the 1,168 local cases tallied.

The numbers bring the average number of patients diagnosed daily in greater Seoul to 636.3 between Thursday and Wednesday — a jump of 36.9% from the week before.

“We’re entering a new wave,” CDCH general situation team director Bae Kyung-taek said Wednesday.

Greater Seoul residents in their 20s and 30s were found to be a core factor in the recent rise.

An examination at the level of Seoul districts showed the average rate of confirmed cases per 100,000 people to total 8.9 for Gangnam, 7.9 for Jung (Central), 6.2 for Yongsan, 5.5 for Jongno, 4.1 each for Seocho and Yeongdeungpo, and 4.0 for Mapo. The district of Ilsandong (Ilsan East) in Goyang, Gyeonggi Province, also had a rate of 4.0 per 100,000.

Lee Ki-il, first control officer for the Central Disaster and Safety Countermeasures Headquarters (CDSCH), said Wednesday that “patient numbers have been rising very sharply for the densely packed areas often used by younger demographics, including bars and nightlife establishments.”

It was also determined that major variants with high transmissibility have been spreading at a rapid rate among the younger greater Seoul area residents driving the recent wave.

“During the second week of June [June 6–12], the detection rate for the Delta variant was 1.8% among people in their 20s. That was up to 17.1% by the fifth week of June [June 27–July 3], and it also rose to 14.9% over the same period for people in their 30s,” Lee Ki-il said Wednesday.

The Delta variant detection rates for people in their 20s and 30s were higher than the 9.9% average rate for all domestic confirmed cases over the same period – and even the 12.7% detection rate when cases were narrowed to the capital region.

The Alpha variant, which is also more transmissible than previous strains, was found to account for 26.6% of confirmed cases in greater Seoul during the fifth week of June. Analysts said the Alpha and Delta variants have significantly influenced the recent wave as they have spread among people in their 20s and 30s who have yet to receive a single vaccine dose.

The explosive rise to over 1,000 daily confirmed cases further suggests a strong possibility that the influence of variants will continue to grow.

“Based on detection rates [to date], the Delta variant hasn’t been driving [the current wave], but from our examination of certain [cluster infections], we believe it is highly transmissible,” said Lee Sang-won, who heads the CDCH epidemiological research and analysis group.

“It’s impossible to predict what [the detection rate] will look like a week from now, but it could remain at the current level or go even higher,” he predicted.

Based on the large number of confirmed cases among relatively widely active young people and the influences of the Alpha and Delta variants, some predict the wave could grow even larger as the basic reproduction number (R0, indicating the average number of additional people infected per confirmed case) climbs.

“If we let down our guard, the number of daily confirmed cases could reach 1,500 or 2,000,” said Park Young-joon, head of the CDCH epidemiological research team.

The central government also began taking emergency disease control measures Wednesday in response to a number of cases at its government complexes in Seoul, Sejong, and Gwacheon.

The Ministry of the Interior and Safety announced the positive diagnoses of a Personal Information Protection Commission employee at the Seoul Government Complex, a Ministry of Employment and Labor employee at the Sejong Government Complex, and an Integrated Government Call Center employee at the Gwacheon Government Complex.

The offices and shared spaces used by the employees were sterilized, and other employees working on the same floor underwent COVID-19 testing, the ministry said.

Another 37 recruits tested positive at the Korea Army Training Center in Nonsan, South Chungcheong Province.

By Choi Ha-yan, staff reporter

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