Hunter Ronson 2016-11-16 11:24:30
In August 1976, the US Centers for Disease Control conducted their largest, most urgent epidemiological response to date. Dozens of physicians and infectious disease specialists scrambled to Philadelphia, PA, the site of a recent American Legion convention, and to sites across the country to where Legionnaire attendees had returned home. A startling number of them were now sick from a previously unknown respiratory illness, and a frighteningly large proportion of the sick were dying. The outbreak made headlines, but the epidemiologists were able to allay panic with a simple observation that became clear almost at once: family members and caretakers of the Legionnaires weren’t falling ill. The disease, whatever it was, wasn’t transmitted from person-to-person. Focus shifted to environmental causes, and in particular to the Bellevue-Stratford Hotel which had hosted the convention. It would be a further six months before a new bacterium, Legionella pneumophila, was identified, years before the transmission mechanism was fully understood. What we now know about L. pneumophila bacteria and the spread of Legionnaires’ disease is of top-tier concern for facilities managers and operators of process cooling systems worldwide. The bacterium that causes Legionnaires’ disease can live in soil, but it thrives in water—particularly in tepid, stagnant water of 68°F to 122°F (in theory, this makes any standing body or water reservoir a possible source of contamination, and indeed the Legionella bacteria has been found in spas, whirlpools, even decorative fountains). In practice, one of the most common breeding grounds, one most rife for spread of the disease, and a common source of deadly outbreaks, are cooling towers and building HVAC systems. Lacking the necessary decontamination protocols; systems such as central air conditioning, evaporative cooling towers, and industrial humidifiers can be seen as the perfect vectors for the incubation and spread of Legionnaires’ disease. The systems’ closed water reservoirs form the ideal breeding media for the bacteria, with the outlets and interior building vents releasing mist, vapor, and aerosolized droplets of the infected water. Once inhaled, the bacteria settle within lung tissue and begin reproducing. Within as little as two days, the victim begins exhibiting symptoms of pneumonia or severe influenza––fever, chills, and respiratory distress. The disease responds to antibiotics if treated promptly. If treatment is delayed or those infected are at risk from severe respiratory disease, mortality rates can approach 30%. Remediation from a process-cooling point of view is straightforward, and is centered upon following the cooling tower and HVAC equipment manufacturer’s guidelines for water treatment and decontamination. Precise guidelines vary, but should all include routine inspection and bacterial analysis, water treatment with biocides and rust inhibitors, and complete drainage, cleaning, and refilling of the system at least twice per year. Another solution—as has been mandated across Europe specifically to address the risk of Legionnaires’ disease—is to replace traditional evaporative cooling towers with no-reservoir systems, such as hybrid adiabatic cooling towers, which utilize a fine mist spray of water during cooling cycles, and is drained and refreshed with each use. Given these solutions, our understanding of the risks, and remediation of Legionella bacteria, one would expect the disease to be on the decline. Unfortunately, recent history does not support this: • Bronx, New York; July–September 2015: separate outbreaks in three neighborhoods result in at least 140 cases of Legionnaires’ disease and 13 deaths. • Porto, Portugal; September 2015: 16 cases of Legionnaires’ disease, 15 hospitalizations. • Quebec, Canada; August 2015: 18 cases of Legionnaires’ disease, two deaths. • San Quentin State Prison, California; August 2015: at least 101 cases of Legionnaires’ disease. • Quincy, Illinois; August 2015: an outbreak at a veterans’ nursing facility results in 54 cases of Legionnaires’ disease and 12 deaths. • Sydney, Australia; March 2016: 50 cases of Legionnaires’ disease and two deaths. Outbreaks of Legionnaires’ disease since the year 2000 have sickened at least 2,100 people, and have killed at least 98. In the vast majority of these outbreaks, water sources, cooling towers, and air-conditioning systems were eventually identified as the infection sources. Reducing infectious risk for visitors, employees, and associates must be of the highest priority to business owners, facilities managers, and process-cooling engineers. Following minimum bacteriological remediation protocols can be seen as both an investment in routine maintenance of property, and as a matter of life and death. The following are general guidelines only—please be sure to follow manufacturers’ recommendations. • Thoroughly inspect cooling system components at least once per month. • Perform monthly bacteriological analyses, checking for system contamination. • Drain and clean cooling reservoirs at least twice per year (every three months if cooling is used year-round). • Treat circulating water with biocides and rust inhibitors as per manufacturer’s specifications. Use continuous-feed systems where possible. • Consider replacing traditional cooling towers with no-reservoir, hybrid adiabatic systems. As a result of the summer 2015 outbreaks in New York, a citywide effort is underway to disinfect cooling systems and to establish more stringent guidelines for the detection and prevention of Legionnaires’ disease. This, along with widespread renewed attention to the disease and its causes, are relatively positive outcomes to be contrasted with the illness, suffering, and loss that was borne by those directly affected by the outbreak. A much better outcome, of course, would be to mitigate the risk and stop the disease before a single person is infected. This is by no means impossible or even inordinately challenging. We know how the L. pneumophila bacterium propagates and is spread, and we know how to eliminate it. We know that care and maintenance of water supplies and cooling systems are the frontline tactics in this public health battle. For nearly 40 years Legionnaires’ disease has been a pernicious cause of severe illness and unnecessary death. It need not be so any longer. This scourge can be eliminated with the diligent intervention of engaged, informed facilities managers and process cooling engineers. DE Hunter Ronson works for NIMBUS Advanced Process Cooling.
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