Health authorities are raising alarms as Legionnaires' disease cases in South Korea surged more than 56% from a year earlier.
A total of 247 cases were reported nationwide from January through April this year, up 56.3% from 158 in the same period last year, according to the Korea Disease Control and Prevention Agency's infectious disease portal on the 6th. Last year's annual total of 599 cases was the highest since record-keeping began in 2001.
Because cases typically peak in July and August, analysts say this year is likely to set another record.
Legionella bacteria multiply rapidly in warm, stagnant water found in cooling towers, bathhouse tubs and fountains. Infection occurs through the respiratory tract when the bacteria disperse into the air as fine water droplets.
The Seoul Institute of Health and Environment inspected about 2,200 public facilities from April through August this year and found Legionella bacteria at one in 10. Department stores and large shopping malls had the highest detection rate, followed by bathhouses and jjimjilbang saunas, then large buildings. A quarter of this year's 509 total cases occurred in Seoul.
The problem is that the symptoms are so common that early treatment is easily missed. In the early stages, fever, coughing and sore throat are difficult to distinguish from influenza. But if left untreated past the window for antibiotics, the illness can progress to a pneumonia form with a fatality rate of up to 80%. From 2020 through 2024, 110 people died of Legionnaires' disease.
Experts stress that while healthy adults may experience only mild fever, older adults and people with weakened immune systems can develop sudden pneumonia, and should see a doctor immediately if symptoms appear.
To prevent infection, it is important to check ventilation when using public facilities and to confirm whether indoor hot water and cooling systems are regularly inspected. Anyone who develops a cough or fever after visiting a bathhouse or sauna should go to a hospital immediately and be tested for Legionnaires' disease.
The disease agency, noting that Legionnaires' disease is designated a Class 3 notifiable infectious disease, recommends that anyone with suspected symptoms report the case and seek diagnosis and treatment. The Seoul city government plans to recommend immediate sterilization and disinfection at facilities where the bacteria are detected, and to conduct up to three rounds of retesting until safety is confirmed.
