The global spread of the Covid-19 Delta variant put additional strains on the quarantine authorities Thursday, although officials remained cautious, saying it is in the early phase of inflow.

Delta has 1.6 times higher transmission power than the Alpha variant and could emerge as a dominant virus in Korea, officials said. According to Central Disaster and Safety Countermeasures Headquarters and foreign reports, more than 80 countries have confirmed at least one case of the Delta variant originating from India.

The U.K. has confirmed that 90 percent of its newly confirmed cases are Delta variants. In Portugal, more than 60 percent of new Covid-19 patients in Lisbon, the nation's capital, have tested for the Delta variant as well.

In the U.S., the number of Delta variant cases has doubled every two weeks, with the share of patients infected by it rising to 20 percent.

In Korea, of the 2,225 patients that tested positive for variant cases, the Alpha variant from the U.K. accounted for the most cases with 1,886 patients, followed by the Delta variant (190 cases), Beta variant (142 cases), and Gamma variant (seven cases). In terms of percentage, Alpha and Delta variants account for 84.8 and 8.5 percent of variant cases.

“Korea has confirmed 190 cases of the Delta variant infection, including three local infection cases, meaning it is still in the early stage of inflow,” Korea Disease Control and Prevention Agency Commissioner Jung Eun-kyoung said.

As the Delta variant is spreading rapidly worldwide, Korea also has to step up measures to block overseas inflows and domestic spread, Jung added.

Among those who arrived from India, the number of people infected with the Delta variant has risen to 190 in two months since the nation reported its first nine cases in mid-April.

Despite concerns over variant cases, the government believes that vaccination can prevent the spread of variant cases, including the Delta mutation, to some extent.

"The Delta-type mutation is rapidly becoming the dominant form worldwide. As it has a higher transmission power than that of the alpha variants, it is a very worrisome situation," said Lee Sang-won, chief epidemiologist at the Korea Disease Control and Prevention Agency (KDCA). "The best countermeasure against variant cases is to complete the vaccination according to a set schedule."

Lee stressed that among U.K. citizens newly confirmed Delta variant cases, 89.6 percent have not completed the second dose, and 65 percent have not received any vaccines at all.

"Therefore, the government believes that there is a significant preventive effect for those who have completed vaccination," Lee added.

The government has vaccinated 15,150,121 people – 10,384,423 with the AstraZeneca vaccine, 3,636,252 with Pfizer's vaccine, 1,125,361 with Janssen's vaccine, and 4,085 with Moderna's vaccine – with the first shot of the vaccine up 28,485 from the previous day.

The figure accounts for 29.5 percent of the country's population.

On Thursday, the country continued to confirm a daily Covid-19 tally of over 600 as cluster infections involving churches, restaurants, gymnasiums, and hospitals continued to occur across the country.

The KDCA confirmed 610 new virus cases, including 576 local infections, raising the cumulative caseload to 153,155.

One more person died of Covid-19, raising the death toll to 2,008 with a fatality rate of 1.31 percent. A total of 144,788 people have returned to their daily life after full recovery, up 409 from the previous day. As a result, the country's total test number has surpassed 10 million, accounting for about a fifth of the country's population. It has carried out 10,438,782 tests since Jan. 3 last year.

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