Industry Insight: A Look at Legionella

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With 12 reported deaths and over 100 illnesses, New York City’s recent Legionnaires’ disease outbreak has many building owners and operators wondering what they can do to prevent it. H2M’s own Paul Ponturo has offered up his expertise in handling legionella-related concerns to help answer some of the common questions you may have. How did Legionnaires’ disease gets its name? Legionnaires’ disease, also called legionellosis, was originally uncovered in an outbreak that occurred at a Bicentennial American Legion celebration in Philadelphia in 1976. Approximately 221 attendees fell ill and 34 died. Legionella bacteria was discovered in the lung tissue of a victim and in the cooling tower of the hotel hosting the convention. What is Legionnaires’ disease? It is a form of pneumonia caused by legionella bacteria. Legionella are widespread in natural water, and also found and distributed in man-made environments. About 48 legionella species have been identified with approximately half associated with human disease. One species, L. pneumophilia, is the most common causative agent in human legionella infections, and is regarded to be the most virulent, accounting for approximately 90% of cases. Is the disease really that common? Nationally, the Center for Disease Control (CDC) reports that legionellosis incidence rates increased threefold between 2000 and 2009, and estimates that 8,000-18,000 people are hospitalized annually. Over $34,000 in direct healthcare costs are estimated to be associated with each case in the United States. All states currently report any occurrence of legionellosis to the CDC. Since 1986, the New York State Department of Health (NYSDOH) has required all legionella cases to be reported to the local health department where the patient resides, and any possible or definite healthcare facility-associated case must be reported to the NYSDOH. Health care and hospital cases (often described as “nonsocomial”) in New York range from less than ten to about 40 cases reported annually. How does it spread? Legionella transmission to humans depends on three main factors. The first is amplification, which most often describes the substantial increase in the concentration of legionella organisms. Conditions frequently associated with amplification include favorable water temperatures (generally between 77-108o F), stagnation, scale, sediment, biofilms, and presence of free-living amoeba. Legionella bacteria are natural inhabitants of water, and can be found in rivers, lakes and streams. The second is the mechanism of dissemination, which is usually aerosolization of the water in which the organism has proliferated. Aerosolization has been associated with a number of devices, including showers and sinks, whirlpool spas, humidifiers, and respiratory care devices such as nebulizers, cooling towers, evaporative condensers, and decorative fountains.

The third is the host’s susceptibility to infection. Those most susceptible are the elderly, smokers, and individuals with chronic lung disease, with the immunocompromised/immunosupressed being particularly at-risk. How can you protect your facility against an outbreak? Occurrence is usually caused by controllable conditions, and the frequency of litigation and monetary settlements reportedly have increased over the years. Many of these legal cases centered on the contention that proper operation and management of facility environmental systems could have avoided instances of disease. Anyone familiar with press reports will note the emphasis on cooling towers as potential sources and sampling and cleaning/disinfection as mitigation. This emphasis is certainly an appropriate response to what is clearly an outbreak of significance, as well the epidemiological findings in this specific outbreak. From the standpoint of approaching preemptive control of growth, it is necessary to recognize that other potential sources in large buildings must be considered—particularly domestic hot water recirculation systems. Many of these systems are designed to circulate hot water at non-scalding temperatures, which often means that all or portions of these systems operate within the ideal breeding temperature for legionella of between 77 and 115o F. Because a number of disease risk issues relate directly to the built environment, they can also be influenced by engineering design, and operation and maintenance practices. There is a growing consensus that the focus should be on acting preemptively to evaluate buildings, with an eye towards minimizing risk. Design, operation and maintenance steps should focus on as many locations in a building as possible to create a series of control mechanisms to prevent disease transmission. What is needed to advise a building owner in development of a risk management plan are skills in engineering, health, safety, building services, hydraulics and microbiology. Additional state regulations, including requirements for cooling tower registration, sampling, disinfection and maintenance, went into effect on August 17, 2015. The New York State requirements and registration process can be found at : Paul Ponturo, P.E. is a Water Resources Engineer for H2M Water. He has expertise and knowledge of handling legionella-related concerns, and can assist with basic consultation, assessment and sampling, and development of proactive maintenance plans to combat legionella growth. You can reach Paul at