BACKGROUND: Legionnaires’ disease is associated with manmade water sources such as cooling towers, spas, and decorative fountains. Interviewing cases thoroughly may identify likely infection sources. In mid-November 2016, an interview with a Legionnaires’ disease case’s proxy revealed that the case worked at a plastics manufacturing facility. Review of surveillance data revealed 2 prior reported cases, with onsets in 2014 and 2011, had also been employed at the same facility. An investigation was begun including additional case finding and review of the manufacturing plant and processes.
METHODS: The facility identified a fourth case with onset 9 days prior to the 2011 case in a Wisconsin resident; Wisconsin local public health interviewed the case but interstate notification with Minnesota did not occur. The facility was contacted and an onsite health hazard evaluation with NIOSH staff scheduled.
RESULTS: The 4 cases were all male, age range 47 – 63 years. All had been hospitalized, all survived, and all were positive by Legionella urine antigen test. All were smokers. All worked as machine operators in the facility which produces thermoplastic pellets. Production necessitates cooling of the plastic as it is being made, generally by water including misters. Multiple water mists and aerosols were identified throughout the plant. The facility installed a water recycling system in 2011 reducing their annual community water intake from 275 to 2 million gallons. Recirculated water is filtered, cooled (to 50-55 degrees F.), and bromine added per system operator’s decision to control bacterial growth. Water is added to the system to make up for loss due to evaporation.
CONCLUSIONS: Intensive interviewing and constant comparison of case exposures revealed a cluster of cases over a 5-year period associated with a single manufacturing facility. No single exposure, but multiple likely exposure sources, were identified. Industrial product production using water for cooling poses a generally unrecognized Legionella risk to workers. A water management plan in such facilities will likely reduce the risk.