2026 Volume 41 Issue 2 Pages 104-108
Our hospital experienced a nosocomial outbreak of Legionella in 2019. After the outbreak was controlled, we continued to conduct monthly water quality testing and infection control measures to prevent nosocomial infection. Initially, we selected approximately 40 sampling sites for water quality testing. After confirming negative results for Legionella over a period of roughly 3 months, we gradually reduced the number of testing sites. For infection control, we maintained hot water storage tanks at 60°C or higher and terminal tap temperatures at 55°C or higher. Flushing protocols were implemented at each water outlet based on usage frequency: for outlets with high usage, we considered that regular flushing occurred through daily use; for those with unknown usage frequency but deemed high risk, we performed daily flushing during cleaning; and for those with unknown usage and considered low risk, we adopted a policy of flushing with hot water (approximately 40°C) for 3 minutes once a week.
Legionella was detected in March, April, and September 2019; January and July 2020; January and April 2021; February 2022; and September 2024. In January 2021, Legionella was detected even after heat disinfection. In response, we installed a shower head with a filter and replaced the shower hose. In all other cases, a single round of heat disinfection was sufficient to achieve negative results. The highest bacterial count detected was 380 CFU/100 mL, followed by 340 CFU/100 mL. In all other cases, the counts ranged from approximately 10-50 CFU/100 mL. We also removed 26 low-use water outlets. No further nosocomial infections occurred, and we concluded routine water quality testing in November 2024.
No suspected cases of hospital-acquired infection have occurred to date owing to continued infection control measures. While water testing is essential during the acute phase of Legionella contamination, after the infection is brought under control, maintaining appropriate water temperatures, preventing stagnation, and performing regular flushing are key measures for preventing nosocomial infections.
