Related Experiment Video
Updated: Jul 8, 2026
Legionella pneumophila Outer Membrane Vesicles: Isolation and Analysis of Their Pro-inflammatory Potential on Macrophages
Published on: February 22, 2017
Legionnaires' disease: evaluation of a quantitative microbial risk assessment model
Thomas W Armstrong1, Charles N Haas
1ExxonMobil Biomedical Sciences, Inc., Annandale, NJ 08801-0971, USA. twa8hr@gmail.com
Background:
The quantities of Legionella vary considerably from natural waters to water in contaminated domestic hot water supplies, whirlpool spas and cooling towers, with the risk for LD rising as the Legionella counts grow. We currently report the results from our Quantitative Microbial Risk Assessment (QMRA) model evaluation. We developed the LD QMRA model to better understand Legionella exposure risks.
Methods:
Using an animal data derived model for LD, we calculated risks from estimated exposures for a whirlpool spa outbreak, two hot spring spa outbreaks and compared the results to the reported LD risks.
Results:
The QMRA model shows agreement (generally less than an order of magnitude discrepancy) with the reported Legionnaires' disease sub-clinical severity infection, clinical severity infection, and mortality risks.
Conclusions:
The LD QMRA model may lead to risk based limits to supplement the current guidance on Legionella control in cooling towers, whirlpool spas and other potential exposure sources. The verification of QMRA for LD also suggests the techniques, given suitable animal model data, may be useful in quantifying human response to other airborne pathogens.
