A new coronavirus flare-up in South Korea is creating a sense of crisis that the worst of the COVID-19 pandemic has yet to come in the winter season, given the faster-than-expected spread of the virus and continued sporadic infections across the nation, and calls are growing over the implementation of further enhanced virus curbs.

The number of new cases spiked to 583 on Thursday, the highest in over eight months, raising the total caseload to 32,318, according to the Korea Disease Control and Prevention Agency (KDCA).

Among them, 553 were local infections, and 402 were reported in the Seoul metropolitan area, home to nearly half of the nation's 51.6 million population.

The latest uptick was comparable to a massive outbreak in the southeastern city of Daegu in February and above the peak in the second wave of infections in Seoul in late August.

Health authorities are repeating their pleas for people to sacrifice their year-end meetings and stay home to slow down the novel virus, expecting the upward trend to continue this week due to sporadic infections from various groups, including the military, workplaces and sports facilities.

They hope stricter distancing measures in the greater Seoul would help mitigate infections.

"The sharp hike in new cases was attributable to several large-scale community infections," Sohn Young-rae, a senior health official, said. "(The number of local infections) is expected to rise until (Level 2) social distancing shows effects starting next week."

Authorities said the country could see 400-600 virus cases daily until early December unless the current pace is curbed, vowing to ramp up antivirus efforts in the winter season.

Experts, however, warned that the recent upward trend may be only the beginning of a bigger pandemic compared with the previous two rounds of massive outbreaks.

Ki Mo-ran, a professor at the National Cancer Center, said the novel coronavirus may have spread at a faster-than-anticipated clip in recent weeks as people increased activities under eased distancing rules, without knowing that they were infected with the virus.

"I think the third wave of the pandemic will spread farther than the second wave of the pandemic in the Seoul metropolitan area, and also be more severe than the first pandemic in Daegu," Ki said, citing a coronavirus model forecasting over 1,000 new daily infections as the worst case scenario. "The key lies in how quickly people reduce contact with other people."

Choi Won-seok, a professor at the Korea University Ansan Hospital, said authorities should expand preemptive testing to discover infections in advance and bring the situation under control.

"The current COVID-19 pandemic is different from the previous cases," Choi said. "The winter season provides a favorable environment for the spread of the virus. If quarantine measures fail to control the recent situation, more cases will be identified."

Choi said "silent spreaders" seem to have contributed to the recent virus resurgence, urging people to minimize social activities to reduce risks of exposure to the virus.

Doctors also expressed worries over the shortage of hospital beds for severely ill patients if the current trend continues, which could paralyze the nation's health care system.

"If the current trend continues for the next several days, hospital beds (for patients with severe symptoms) could run out faster than expected," Kim said.   

According to the KDCA, there were currently 115 hospital beds available for virus patients in critical condition as of Wednesday.

Health authorities have advised those in their 20s and 30s to refrain from informal gatherings and other activities, as they tend to have no symptoms or mild symptoms in the first three or four days of infection, raising the risks of exposure to other people.  

Those in their 20s infected with COVID-19 rose at the fastest clip among all age groups last week, taking up 17.8 percent of new cases, authorities said.    

Some said authorities should take stronger antivirus measures on a national scale to flatten the virus curve before it's too late.

"Sporadic infections have been discovered across the nation since the daily number of patients surpassed 300, making the pace of epidemiological investigations fall behind that of the virus spread," said Kim Dong-hyun, a professor at the Hallym University Medical Center. 

"(Health authorities) should consider upgrading the social distancing guidelines not only in the Seoul metropolitan area but also in other regions in accordance with the recent rise in outbreaks."

To curb the recent virus surge, authorities raised the social distancing level by one notch to Level 2, the third highest in the country's five-tier system, in the Seoul metropolitan area for two weeks starting Tuesday.

Level 2 curbs can be enforced if the country's daily number of local infections exceeds 300 for a week.

The move came as the daily average figure of domestic infections stood at 316.3 in the most recent one-week period, with an average of 222 of them coming from the capital area.   

Other municipalities also have been enforcing tougher distancing rules depending on their virus situation. Level 1.5 distancing is currently in place in Gangwon Province and the country's southwestern Jeolla region.

Authorities, however, remained cautious over further raising the distancing level to Level 2.5, which is imposed when daily new cases continue to surpass 400-500 nationwide or the number of patients double from the previous day.

Under Level 2.5 measures, companies and organizations are required to recommend that over one-third of employees work from home. Gatherings of over 50 people are banned, and public transportation, such as trains and express buses, are subject to a 50 percent cap on reservations.

"Today's patient numbers do not meet standards for Level 2.5 distancing, and it is too early to tell the effectiveness of Level 2," Sohn said. "We will continue to discuss the matter, while keeping an eye on the effect of the recent hike in social distancing guidelines." (Yonhap)