Cooling towers have been linked to outbreak-related and nonoutbreak-related legionellosis. Proper cooling tower maintenance and disinfection are imperative for legionellosis prevention but not monitored in Allegheny County, Pennsylvania, which is a high incidence area. To investigate cooling tower maintenance and Legionella positivity, the Allegheny County Health Department (ACHD) performed a survey regarding the presence and maintenance of cooling towers and tested cooling towers for Legionella pneumophila (Lp). ACHD surveyed healthcare facilities, senior apartment buildings, and county-owned buildings.
Associations between maintenance practices and Lp were assessed using Wilcoxon rank-sum tests and multivariable linear regression. Of 408 building managers contacted, 377 (92%) completed the survey and 56 (15%) reported managing a building with a cooling tower. Among 42 cooling towers sampled, 20 (48%) tested positive for Lp. Factors associated with positivity included larger tower capacity, year-round usage, hospital status, and older tower age. Only cooling tower age was associated with Lp after stepwise regression.
Despite maintenance practices, many cooling towers were Lp positive. ACHD recommends that facilities develop a water management plan that is compliant with standards of the American Society of Heating, Refrigerating, and Air-Conditioning Engineers and also conduct annual basin water emptying, quarterly cleaning, and diligent inspection of older towers.