Outbreak of Nosocomial Legionellosis Managed by Adoption of Chlorine Dioxide Infusion System

Abstract

Background: Close surveillance of Legionella in the plumbing systems of medical institutions is required because of the higher morbidity and mortality of nosocomial legionellosis. We experienced an outbreak of legionellosis in a university hospital, managed with a chlorine dioxide infusion system. Methods: Multiple contaminations with Legionella were reported in the annual water surveillance in June 2019. A task force was established to prevent the outbreak of legionellosis, and the entire plumbing system of the hospital was investigated. Initial measurement was done according to the action manual of the Korean Disease Control and Prevention Agency, including cleaning of hot water tanks, superheating and flushing, point-of-use management (change of showerheads and taps on washstands), and application of filters in higher-risk areas. Further shock hyperchlorination for the cooling tower and cleaning of the water tank were performed since persistent contamination was reported in these areas. Nevertheless, there was an outbreak of three presumable cases of in-hospital legionellosis. A continuous infusion of chlorine dioxide (ClO 2 ) was planned to decontaminate the hospital's plumbing. Equipment for ClO 2 infusion was installed by May 2020, with terminal monitors of residual chlorine and a feedback system. A repeated environmental culture study was also planned. Furthermore, a preemptive surveillance system including active monitoring for patients tested with Legionella urinary antigen was developed, and a newer response manual for legionellosis was distributed. Results: Isolation of Legionella in hospital water was first noted in June 2019. Since then, Legionella has been identified in 6 out of 47 samples in five surveillances by the public health center. Furthermore, 6 out of 85 samples were reported to be positive for Legionella by inhospital water cultures. Two patients were diagnosed with nosocomial legionellosis within 3 months of the initial response. After the installation of the ClO 2 continuous infusion system in May 2020, no isolation of Legionella was reported in the next two whole environmental surveillance. No further cases of bacterial inoculation or Legionella infections have been reported so far. Conclusion:The outbreak of nosocomial legionellosis was successfully terminated with the continuous infusion of ClO 2 into the premise plumbing system of the hospital. Sporadic outbreaks