The Role of Aspiration in Legionnaires’ Disease: A Quantitative Microbial Risk Assessment (QMRA)-Based Comparison with Inhalation Exposures

Abstract

Legionellosis is generally attributed to the inhalation of aerosolized Legionella pneumophila from engineered water systems and/or soils. However, aspiration of contaminated water─a known cause of aspiration pneumonia─is seldom modeled in L. pneumophila risk assessment. Here, we develop a quantitative microbial risk assessment model to estimate the risks associated with aspiration exposures. Monte Carlo simulations, incorporating the aspiration water volume, the aspiration frequency, and the alveolar deposition fraction, reveal that low L. pneumophila concentrations in water can yield an appreciable infection risk in populations prone to aspiration. Under equal L. pneumophila concentrations, we find that an aspiration event can pose a higher infection risk than aerosol inhalation from showers or faucets. Sensitivity analyses identify the aspiration volume as a driver of risk. Our findings highlight the need for risk management strategies that address not only aerosol generation but also the aspiration of contaminated water.