South Korea’s new daily COVID-19 case count soared to 583 on Thursday, the highest single-day increase in virus cases since early March amid a full-blown third wave of infections across the country.

The country reported 553 locally transmitted cases and 19 cases imported from overseas in the 24 hours ending Wednesday at midnight, according to the Korea Disease Control and Prevention Agency.

It is the first time that the country’s daily virus cases have exceeded 500 since March 6, when the figure stood at 518 amid the first wave of infections triggered by a branch of a small religious sect in Daegu. Thursday’s case tally marks a spike from 382 cases a day earlier, 349 on Tuesday and 271 on Monday.

Korea is experiencing a full-blown third wave of infections, with virus outbreaks taking place nationwide simultaneously, sources of infections diversifying, and the major age groups being affected shifting from older to younger populations, according to the KDCA.

“Korea is battling the full-blown third wave of infections. We may see 400 to 600 new daily COVID-19 cases until early December, according to a result of mathematical prediction analysis,” Lee Sang-won, a senior official at the KDCA, said at a briefing Thursday.

If the tougher social distancing measures in the Greater Seoul area begin to show the impact, the infection rate could begin to slow next week and the country could reach a peak at the end of next week, he added.

The capital area has been under Level 2 social distancing measures -- the third highest in the country’s five-tier system – since Tuesday.

New clusters of infections are being reported from places people visit every day -- ranging from workplaces and schools to indoor sports facilities and restaurants -- which complicates the government’s contact tracing efforts.

On Thursday, a new cluster of infections was traced to a dance studio in western Seoul, with a total of 66 people infected. The first case was reported Monday. Another cluster of infections was linked to a district office in northern Seoul, with 15 cases detected so far. In connection with a military barracks in Yeoncheon, Gyeonggi Province, 68 have soldiers tested positive for the virus since the first case was confirmed Wednesday.

According to the KDCA’s analysis on coronavirus infections reported over the past two weeks in Korea, the majority of the new infections were from the Greater Seoul area -- Seoul with 36.7 percent, Gyeonggi Province with 24 percent and Incheon with 5.3 percent -- home to half of the country’s population.

Cities and provinces outside the Greater Seoul area saw smaller outbreaks, with 5.7 percent of the cases reported for the past two weeks having been posted in Gangwon Province, 4 percent in South Jeolla Province, 3.7 percent in South Gyeongsang Province and 3.6 percent in South Chungcheong Province.

Looking at transmission routes for the cases reported during the past two weeks, 40.4 percent of those involved were infected with the virus in connection with clusters, 27.1 percent after coming into contact with confirmed patients and 10.8 percent after coming to Korea from overseas, according to the data.

As of Thursday, the transmission routes for 14.7 percent of the cases reported from Nov. 13-26 remained unknown.

Of Thursday’s locally transmitted cases, the majority were in Greater Seoul -- 208 in Seoul, 177 in Gyeonggi Province, which surrounds the capital, and 17 in Incheon. Outside the Seoul metropolitan area, cases were registered in all cities and provinces.

Of the 30 imported cases reported Thursday, 12 were detected at the border, while the other 18 were identified in individuals under mandatory self-quarantine in Korea. Eleven cases were from elsewhere in Asia, while eight were from the Americas, six came from Europe and four were from Africa.

Sixteen of those cases involved foreign nationals.

The number of COVID-19 patients in serious or critical condition here stood at 78.

Two more people died from the virus, bringing the death toll to 515, with the overall fatality rate at 1.59 percent.

So far, of the 32,318 people confirmed to have contracted the new coronavirus here, 26,950 have been released from quarantine upon making full recoveries, up 125 from a day earlier. Some 4,853 people are receiving medical treatment while under quarantine.

The country carried out 21,641 tests in the past day. A total of 55,361 people were awaiting results. 

By Ock Hyun-ju (laeticia.ock@heraldcorp.com)