As the fourth wave of Covid-19 shows few signs of easing, health officials expressed concerns Monday that the Delta variant, which has strong contagious power, will soon emerge as the dominant strain in Korea, too.

"Last week, the detection rate of the Delta variant rose to 48 percent of all infected cases and has since been increasing rapidly. We can objectively predict that it will exceed 50 percent this week," Ministry of Health and Welfare Spokesperson Son Young-rae said.

Son stressed that Delta variant cases, once dominant mainly in the Seoul metro region, are spreading to the rest of the country.

According to the quarantine authorities, the detection rate of the Delta variant was only 3.3 percent in the fourth week of June. However, it rose to 48.0 percent in the third week of July, a 44.7 percentage point increase in about a month. The quick rise in Delta cases has beat the estimates of quarantine officials who had expected it would not become a dominant virus until August.

However, Son noted that there would be no significant changes in response to variant cases.

"Variant viruses are not much different in transmission pattern," Son said. "While variant cases have a fast and powerful propagation speed, it does not have different characteristics as the original virus, in its infection pattern or the showing of higher transmission power for a certain group."

In a situation where the transmission characteristics are not different, the quarantine response strategy does not change, he said, adding that the government keeps closely monitoring the variants’ spread.

"The government is judging that there is a problem that we are missing from the usual intensity of social distancing or quarantine response strategies," Son said. "An increase in the proportion of Delta variant cases means that the Delta variant is the only strain spreading while the current quarantine measures or social distancing measures are sufficiently suppressing the existing Covid-19 infection."

Therefore, there need to be efforts to block the spread through stronger and faster measures than before, he added.

The spread of the virus in non-Seoul regions has recently been a problem, as vacationers travel to tourist spots across the country in the summer season, with some 40 percent of newly reported cases coming from non-capital regions.

To stem the spread of the virus, Korea extended the highest distancing measures of Level 4 in the Seoul metropolitan area for another two weeks through Aug. 8. The most rigid distancing restrictions ban gatherings of more than two people after 6 p.m. and place a 10 p.m. curfew on restaurants and cafes and a ban on nightclubs and other entertainment venues.

The country also decided to enforce Level 3 distancing restrictions in the non-capital areas from Tuesday until Aug. 8 to contain the virus during the summer holiday season better.

Under Level 3, cafes and restaurants can accept customers until 10 p.m., and only takeout and delivery services are available after that time. Private gatherings of more than five people are banned, while mass-gathering events can accommodate less than 50 people.

Commenting on the latest upgrading of social distancing steps, Son said. "The transmission speed itself is considerably faster than the second and third viral wave, so we upgraded the measure so that we can remove hidden infections and silent transmission in the community."

The country added 1,318 Covid-19 cases, including 1,264 local infections, raising the total caseload to 190,166, according to the Korea Disease Control and Prevention Agency (KDCA). The figure was down from 1,487 on Sunday.

The daily caseload has remained above 1,000 for 20 days since July 7 due to the resurgence in the greater Seoul area. The coronavirus has been spreading across the nation with increased activities in the summer season and the fast rise of the highly contagious delta variant. Four more people died from the virus, raising the death toll to 2,077 with a fatality rate of 1.09 percent.

The government has vaccinated 16,893,124 people – 10,404,157 with the AstraZeneca vaccine, 5,295,975 with Pfizer's vaccine, 1,129,722 with Janssen's vaccine, and 63,270 with Moderna's vaccine – with the first shot of the vaccine up 1,492 from the previous day.

The figure accounts for 32.9 percent of the nation's population.