Healthy Indoors Magazine - USA Edition

Legionella Continued from previous page Healthy Indoors 37 Dr. David Krause, the national practice leader for building health sciences at Consultants, holds a Doctorate in Environmental and Oc- cupational Health and Masters of Science in Public Health from the University of South Florida. He has 20 years of experience in envi- ronmental science and public health, focusing in the areas of toxicology, occupational health, industrial hygiene, indoor air quality, and chemi- cal emission testing. Prior to joining, Dr. Krause served as the State Toxicologist for the Florida Department of Health and lead efforts to inves- tigate potential public health risks associated with corrosive Chinese drywall and the Deep- water Horizon Oil Spill. He the 2009 Florida DOH Guidelines for the Surveillance, Investiga- tion, and Control of Legionnaires' Disease in Florida. David is a Certified Industrial Hygienist with expertise in combustion products, flame retardants, irritant chemical exposures, indoor air quality, Legionnaires disease, and mold. to human transmitted illnesses such as Tubercu- losis, but may not best fit Legionnaires' disease. Because LD is a building related illness with am- plification sites and exposure pathways that are readily detectable with environmental monitoring, we can intervene earlier in the disease process. A different model for early detection and pre- vention should be considered for Legionnaires' disease. MORE RESEARCH IS STILL NEEDED A global approach to control, investigation, and prevention of LD has not been adopted by Public Health organizations due to technical, practi- cal, and jurisdictional hindrances. Uncertain- ties about interpretation of Legionella sampling data, its habitat and infectious virulence have made efforts to develop standards on preventing building water system colonization controver- sial. Despite volumes of research on Legionella much still remains to be learned. How to reliably monitor and control its amplification by habitat modification is among the most critical pieces of information we need to discover. This organ- ism is difficult to study and even more difficult to control. Legionella has demonstrated its great resilience and the ability to adapt to disinfectant regimens. Legionella seems to develop some tolerance to disinfectants through a variety of survival mechanisms. This should not be in- terpreted as becoming resistant to disinfection through biochemical or physiological changes in the organism. Rather, Legionella tends to find ways to escape eradication measures by hiding and symbiosis with other waterborne microbes. Legionella has also been seen to increase its virulence, or its ability to cause infection. This appears to be related to a survival mechanism practiced when living among amoebae and protozoa. Its ability to adapt to its environment means that building operators must remain vigilant against Legionella. Its ability to colonize environments and water systems that most other bacteria cannot often surprises building opera- tors. RECOMMENDATIONS FOR POTABLE WATER SYSTEMS So what are the current industry practices and public health recommendations for the surveil- lance and prevention of Legionnaires' disease in non-healthcare potable water systems? The most definitive thing you could say is that "it de- Some of the limitations and difficulties surrounding the investigation of Legionella and Legionnaires' disease have been recognized by the CDC in their own reports. • "Urine antigen tests were used to confirm 97% of U.S. resident cases reported dur- ing 2005–2009." • "Only 5% of cases were confirmed by culture during this period, and <1% were confirmed by either serologic or direct fluorescent antigen testing." • The almost total reliance upon urine anti- gen tests to confirm LD hinders investiga- tors trying to link environmental sources with patient disease. This requires molecular or DNA comparison of envi- ronmental isolates with clinical isolates. Without clinical isolates, confidence that the disease-causing sources has been found and remediated is diminished. • "…detection, investigation, and report- ing of outbreaks are incomplete, and the level of surveillance and reporting activity varies across states and localities. Link- ing illness to drinking water is inherently difficult through outbreak investigation methods (e.g., case-control and cohort studies) because most persons have daily exposure to tap water." • "…outbreak surveillance should not be used to estimate the total number of ill- nesses from waterborne disease because most cases of waterborne disease are believed to occur sporadically or as part of outbreaks that are never recognized."

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