Nearly three in ten patients who have died of the new coronavirus in South Korea suffered from dementia, as the degenerative brain illnesses is more common among elderly people, local health authorities said Tuesday.

The country's COVID-19 death toll has risen to 124 as of Tuesday, up 13 from a day earlier, the Korea Centers for Disease Control and Prevention (KCDC) said. Of the total fatalities, 34, or 27.4 percent, had dementia.

"We are making utmost efforts to detect virus patients at an early stage to provide treatment. However, the mortality rate is higher among those older than 65 years old and suffering underlying diseases," KCDC Deputy Director Kwon Jun-wook told reporters.

There is no known correlation between degenerative brain illnesses like Alzheimer's disease and the novel coronavirus, but the pneumonia-like virus has affected elderly people previously treated at medical facilities, such as nursing hospitals, the most.

"The novel coronavirus is usually related to respiratory and digestive organs," Woo Heung-jeong, an infectious disease expert, said. "There has not been a report that says COVID-19 affected brain function or caused neurological symptoms."

South Korea's mortality rate stood at 1.33 percent on Monday, according to the KCDC. For those aged 80 and above, the fatality rate was much higher -- 12.84 percent.

Health authorities further said the analysis is mainly because many of elderly people, most notably those aged 80 or over, suffer from dementia.

"Various factors affected the data as many of the country's COVID-19-related deaths were not only elderly but also were already very ill," Yoon Chang-ho, a neurologist at Seoul National University Bundang Hospital, said.

The COVID-19 mortality rate in South Korea was around 0.6 percent in early March and gradually increased to 0.8 percent in mid-March before breaching 1 percent this week, the KCDC said.

The country's COVID-19 death rate is lower than the average 4.9 percent mortality rate tallied by the World Health Organization and Italy's fatality rate of more than 9 percent.

The KCDC said the underlying diseases involved in local deaths vary. Among them are cancer, pneumonia, dementia, diabetes and high blood pressure, and most of the deceased suffered from at least one preexisting ailment, sometimes two

"Further study is under way into the ratio of other underlying diseases suffered by all of confirmed COVID-19 patients," Kwon said.

The country's new virus cases appeared to be steadily decreasing Tuesday, but imported infections saw their biggest one-day increase as the nation enforced quarantines on arrivals from Europe and other regions.

The 76 new cases, which were detected Monday and were slightly up from the 64 new cases a day earlier, brought the nation's total infections to 9,037, the KCDC said. (Yonhap)