Medical workers put COVID-19 test kits on a table at a testing booth set up in a rest area near a highway in Yongin, 40 kilometers south of Seoul, on Sept. 7. Yonhap

A simultaneous outbreak of COVID-19 and the seasonal influenza, dubbed a "twindemic," could hit Korea over this fall and winter, experts warned Monday, calling for a thorough medical response system to be in place in the event of such an outbreak.

The number of patients showing possible flu symptoms came to 4.7 for every 1,000 outpatients between Aug. 28 and Sept. 3, rising steadily from 3.3 tallied four weeks earlier, according to latest data compiled by the Korea Disease Control and Prevention Agency (KDCA).

The figures for people aged under 50 ranged from 5.2 to 8.5, already surpassing the threshold of 4.9 expected for the 2022-2023 season, the data showed.

Korea's COVID-19 cases have been falling in recent months after peaking at around 180,000 in mid-August as the latest wave of an omicron variant has been slowing down. On Monday, the country reported 36,938 new infections.

Health authorities, however, have called for people to stay vigilant, as the country is about to enter the first winter season without social distancing rules since the COVID-19 outbreak. The four-day Chuseok fall harvest holiday, which ran from last Friday, has also been cited as a potential trigger for another virus spike.

Experts raised concerns that the scenario of a COVID-19 surge coinciding with the spread of flu could cause big confusion among citizens and also result in a rapid increase of serious cases that could affect the medical system nationwide.

"If we have a twindemic, we need to be able to detect whether it's COVID-19 or not, but the antigen tests have limitations," Kim Tak, a medical professor at Soonchunhyang University Bucheon Hospital, said.

Medical experts called for the need to have thorough procedures ready to detect and treat the diseases under a twindemic situation and possibly consider introducing a polymerase reaction (PCR) test designed to detect the flu and COVID-19 at the same time.

They also urged the authorities to draw up a vaccination plan for people to be able to get the COVID-19 and flu vaccines together. (Yonhap)