Following the confirmation of the first case of XL, a recombinant of the Omicron Covid-19 strain, in Korea, health authorities have detected the XE and XM mutations for the first time.
A recombinant variant occurs when two or more variants simultaneously infect an individual.
The Central Disaster and Safety Countermeasures Headquarters (CDSCH) said Tuesday that health officials have confirmed two recombination mutation XE cases and one XM case and are conducting an epidemiological investigation.
One of two cases of XE infection originated from the U.K., with the patient testing positive on March 27. The other XE and XM patient tested positive after undergoing tests in Korea on March 30 and 27. Infected persons showed symptoms early but showed no specific symptoms to distinguish them from the existing virus. As a result, they have been released from quarantine.
However, officials stressed that the two new infections by XE and XM were confirmed here, not flowing in from abroad.
"There is a possibility that the two cases were due to transmissions through overseas inflows. However, considering the current circumstances, we also cannot rule out the possibility of the occurrence of XE and XM in Korea and are conducting investigations," said Lee Sang-won, head of the epidemiological investigation and analysis team at CDSCH.
The XE mutation is the recombinant of Omicron BA.1 and BA.2, with a 10 percent higher transmission speed than BA.1. According to the World Health Organization, 489 cases have been found in four countries, including the U.K., U.S., and Ireland, since January. They have since been confirmed in Asian countries, such as Taiwan, Thailand, and Japan.
Korea's daily Covid-19 tally jumped back to a six-digit figure on Tuesday, but the Omicron variant was slowing down as the tally nearly halved compared to the average of a week ago.
The Korea Disease Control and Prevention Agency (KDCA) confirmed 118,504 new virus cases on Monday, raising the cumulative caseload to 16,471,940.
The death toll came to 21,354, up 130 from the previous day, with a fatality rate of 0.13 percent. However, critically ill patients came to 834, down 16 from a day ago.
The drops in new virus cases and severe patients follow the government's lifting of most quarantine rules, except for the mask mandate, a major step toward returning to pre-pandemic life from Monday.
Under the eased rules, small businesses can operate without constraints on hours, and people can meet without any limit on the sizes of private gatherings.
The government said it would consider whether to lift the mandatory outdoor mask next week.
The government plans to downgrade Covid-19 from the highest to the second-highest rating in its four-tier infectious disease control system on April 25.
If downgraded, Covid-19 patients will no longer have to undergo mandatory self-quarantine and will be able to receive treatments at local clinics as early as late May.
The transition team of President-elect Yoon Suk-yeol also said that it is considering a plan to expand the target of patients who can receive a prescription for the oral Covid-19 treatments to those with underlying diseases over the age of 12.
As of Tuesday, 33 million people have received booster shots, or 64.3 percent of the country's population. The number of fully vaccinated people also came to 44.53 million, representing 86.8 percent of Koreans, the KDCA said.
On Monday, reservations opened for a second Covid-19 vaccine booster shot for people over 60, four months after their first booster dose.