Reported cases of Legionnaires' disease, often mistaken for a common summer cold due to symptoms such as dry cough, are surging in Korea this year.
According to the Korea Disease Control and Prevention Agency's (KDCA) infectious disease portal on Tuesday, 247 cases of Legionnaires' disease were reported nationwide between January and April this year, up 56.3% from 158 cases in the same period last year. Annual reported cases reached 599 last year, the highest figure since related statistics were first compiled in 2001. Given that cases typically peak in July and August due to seasonal factors, the annual total this year is likely to exceed last year's level.
Legionnaires' disease is a respiratory infection caused by the Legionella bacteria and was designated as a Class 3 statutory infectious disease in 2000. While the bacteria exist at low concentrations in rivers and streams, they multiply rapidly in environments with water temperatures between 25 and 45 degrees Celsius, such as aging pipes inside buildings, cooling tower water, and water supply facilities. The multiplied bacteria spread through the air in the form of fine water droplets and enter the human body through the respiratory tract. Person-to-person transmission generally does not occur.
Clinical manifestations are divided into two types: pneumonia and influenza-like illness (Pontiac fever). The influenza-like form presents respiratory symptoms similar to the flu and usually resolves on its own within a week. The pneumonia form is accompanied by fever, dry cough, muscle pain, and headache, and can lead to respiratory failure in high-risk groups including those over 50, patients with chronic lung disease, and the immunocompromised. Deaths from Legionnaires' disease totaled 28 in both 2023 and 2024.
Health authorities cite rising water source temperatures due to climate change, aging water supply equipment in large facilities, and an increasing elderly population as reasons for the rise in cases. "Cases have been increasing since COVID-19, so we are strengthening facility inspections and monitoring," a KDCA official said. "Thorough inspections are needed at facilities requiring infection source management, and individually, it is advisable to follow basic hygiene rules such as washing hands after going out."
