The number of COVID-19 patients with unclear infection routes is rising, with the authorities failing to identify the source in more than a fifth of cases confirmed in the past two weeks, health authorities said Monday.

According to the Korea Centers for Disease Control and Prevention, the infection route in 22.7 percent of the 4,432 cases confirmed in the two-week period starting Aug. 18 remains unclear. The figure is the highest seen since the authorities began compiling related data in April, and poses a major risk to the country’s quarantine efforts, which rely heavily on contact tracing.

As of midnight Sunday, the number of COVID-19 cases in South Korea stood at 19,947 with 248 individuals being confirmed positive Sunday.

The number of cases per day continues to drop since reaching 441 as of midnight Wednesday. But Sunday marked the 18th consecutive day with a three-digit daily increase.

Seoul and the surrounding regions continued to see the largest numbers, with 91 cases reported in Seoul, 79 in Gyeonggi Province and 13 in Incheon.

Cases linked to Seoul’s Sarang Jeil Church increased by 21, pushing the total to 1,056, while cases linked to an Aug. 15 rally in central Seoul rose by 30 to 399.

At Monday’s briefing, Korea Centers for Disease Control and Prevention chief Jung Eun-kyeong urged the public to adhere to social distancing and hygiene guidelines, stressing that this week will be critical in the country’s fight against the virus.

Saying that the current social distancing measures must be followed strictly to have the desired effect, Jung stressed that despite the fall in daily figures, the situation remains critical with more than 200 cases being reported on a daily basis.

“Still, the number of daily cases remain in the 200 range, and cluster infections are occurring simultaneously across the country,” Jung said.

She said the number of patients in severe or critical condition has more than doubled from last week, reaching 79 on Monday.

“Whether the link of transmission is severed this week by strictly following social distancing measures this week is very important to managing the COVID-19 epidemic in the future.”

The rapid increase in the number of COVID-19 patients in Seoul and the surrounding areas appears to already be taking a toll on the region’s capacity to handle patients, particularly those with severe symptoms.

According to the Seoul Metropolitan Government, 76 percent of hospital beds set aside for COVID-19 treatment in Seoul, Incheon and Gyeonggi Province were occupied as of Monday.

The region’s capacity to treat seriously and critically ill patients is nearing saturation, with only 23 of the necessary 317 hospital beds still available.

By Choi He-suk (cheesuk@heraldcorp.com)