Issue link: https://beckershealthcare.uberflip.com/i/447830
12 Executive Briefing: UV Light Disinfection Thus, similar to the CDC's pathogen hierarchy for manual disin- fectants, examining the UV pathogen hierarchy is a good starting point when determining if a specific device has the potential to support a claim against emerging pathogens. The generalized UV pathogen hierarchy adapted from the "Ultra- violet Germicidal Irradiation Handbook: UVGI for Air and Surface Disinfection" (shown in Table II), provides guidance on the micro- bial susceptibility to UV-C light among various organism species. The hierarchy of susceptibility to UV-C light is notably different than that referenced for chemical manual disinfectants. In general with UV-C, vegetative bacteria are easier to inactivate, and fungi require the highest UV-C dosage for inactivation. Interestingly, bacterial spores such as Clostridium difficile, which are known for their environmental persistence, are intermediate on the UV Dose Hierarchy. Beyond this hierarchy, there is a wealth of data available on the UV dosage required for inactivation of specific pathogens. How- ever, unlike manual surface disinfectants, the EPA does not cur- rently provide a route for obtaining EPA-registered kill claims us- ing UV germicidal irradiation. UV dosages for non-enveloped viral pathogens such as adenovi- rus, norovirus, poliovirus, and rotavirus range from 18,000-84,000 μw-sec/cm² for a 2-log kill. 13 , 14 In comparison, the UV dosage re- quired to inactivate enveloped Ebola virus is significantly less – 2000 15 -5300 16 μw-sec/cm² for a 2-log kill. Historically, UV doses have been listed by either their D90 (90 percent inactivation) or D99 values (2-log reduction). In order to address the more strin- gent needs for healthcare applications, 3-4 log reductions (99.9 percent to 99.99 percent microbial kill) or greater are typically ob- tained for target microorganisms and validated via laboratory test- ing. Comparisons of known and predicted pathogen doses can be used to determine the effectiveness of a UV-C device at a given exposure time and distance. Current limitations for UV microorganism efficacy testing Since there are no EPA-approved protocols to validate micro-effi- cacy claims for UV devices, the industry faces a lack of standard- ized test methods and oversight on the claims made by device manufacturers. Thus manufacturers generate data using different test methods, making it difficult to compare efficacy claims from one device to another for pathogens. Device manufacturers that generate micro-efficacy data should show full transparency about the test conditions used, such as the irradiation time, distance, substrate, carrier load, and density as well as for the log reductions obtained. Building the case for a comprehensive bundled approach: Manual disinfection supplemented by UV-C devices In light of the dangers posed by emerging pathogens, many hos- pitals are interested in emerging technologies such as UV-C tech- nology to reduce transmission to patients and protect their staff. UV devices can add an extra layer of assurance when it comes to terminal cleaning; reaching areas of the healthcare environment that may otherwise be missed or insufficiently addressed due to human error. However manual disinfection is still essential for re- moving soils and killing pathogens on environmental surfaces and plays an important role in infection prevention protocols. A key finding of the 2011 study by Sagripanti and Lytle in the Archives of Virology 17 and work by Bausch published in The Journal of Infectious Diseases 18 is that environmental conditions can impact the effectiveness of pathogen inactivation via UV de- vices. The presence of organic matter, such as dried blood, can shield the pathogen from the UV-C light and reduce the treat- ment's effectiveness. In addition, studies have shown that only 50 percent of high-risk surfaces in healthcare settings are prop- erly cleaned 19 . These studies further illustrate the need for the use of appropriate manual disinfection prior to UV-C treatment. UV-C room treatment serves to supplement, not replace, stan- dard cleaning and disinfection protocols 20 and provides another weapon in the battle against pathogens that cause healthcare- associated infections (HAIs). As healthcare facilities strive to identify novel solutions to meet the infection control challenges posed by emerging pathogens, it is important to remember how to "bridge the gap" to determine which disinfectants and UV devices can be used based on EPA- registered efficacy claims. This can be done by consulting known Table II Generalized UV-C Dose Hierarchy 12 Listed by Decreasing Inactivation Difficulty Fungal Spores Fungal Cells/Yeast Bacterial Spores Viruses Vegetative Bacteria Since there are no EPA-approved protocols to validate micro-efficiency claims for UV devices, the industry faces a lack of standardized test methods and oversight on the claims made by device manufacturers. When an emerging pathogen poses a significant public health risk, the CDC and EPA guidance is intended to bridge the gap by identifying disinfectant products that may be used while effective test protocols are being developed.