Healthy Indoors Magazine
Issue link: https://hi.iaq.net/i/289980
34 April 2013 Legionella Continued from previous page knowledged that cases of Legionnaires' disease are both under diagnosed and under reported. The delays in recognizing outbreaks often mean that investigation by public health agencies and intervention efforts don't begin until the outbreak is over. Criti- cal evidence is often gone or altered and amplification sources have changed. This means that some outbreak investigations have no hope of discovering the source of infection. When this happens it is sometimes difficult for all parties to accept that a clear definitive answer about how the outbreak happened and where the source was cannot be given with certainty. How is sampling data interpreted in these instances when the investigation is per- formed after the outbreak is over? Tying together the clinically diagnosed cases with environmental sources is becoming more difficult due to an "advance" in testing. Overwhelming reliance upon the urinary antigen assay has had an unintended impact on the ability to compare and connect disease with environmental sources. Patients diagnosed only with the UAA test, and not confirmed using culture methods, cannot be compared to environmental isolates using more specific markers. Despite recom- mendations by the CDC to follow a positive UAA test with culture testing, clinicians rarely do. This practice impedes environmental investigations and increases their uncertainty. THE HAZARDS OF RELYING ON SURVEILLANCE The current model for addressing Legionnaires' disease is for public health agencies to perform surveillance. This essentially means that when people have been diag- nosed with LD they are reported to the County or State health departments. More information is then gathered through interviews and all of the information is compiled. If a pattern or trend emerges it might be detected and reported as an outbreak. How- ever, in the vast majority of cases, no association is detected and the information is not (also maybe confirm this unless it makes sense to you – seems like he means to say that the info will NOT be passed to the CDC if no association is detected, right?) even passed along to the CDC. Since surveillance relies upon a significant "body count," nothing happens at county, state, or federal public health agencies until many people are sick or dead. Current practices for most buildings, except certain areas of hospitals, do not include any testing or evaluation of Legionella in their potable or utility water systems. While most facilities with cooling towers perform some type of chemical treatment, it is not common practice to determine if the chemical treatment effectively prevents Legio- nella amplification by laboratory sampling. Despite the dubious nature of surveillance as the first line of defense, the CDC continues to rely upon latent detection of the sick and dying patients. This model of disease prevention may be necessary for human