SPONSOR CPD PROGRAMME Continuing professional development (CPD) is the regular maintenance, improvement and broadening of your knowledge and skills, to maintain professional competence. It is a requirement of CIBSE and other professional bodies. This Journal CPD programme can be used to meet your CPD requirements. Study the module and answer the questions on the final page. Each successfully completed module is equivalent to 1.5 hours of CPD. Modules are also available at www.cibsejournal.com/cpd The control of legionella in wholesome hot-water systems This module considers the challenges of combating increasing risks from legionella in domestic hot-water systems Building operators have a specific responsibility to ensure the safety of building occupants in this period of the Covid-19 pandemic. However, the challenge is to maintain holistic control of all potential hazards that, without suitably applied knowledge and understanding, could create further and significant health issues. This includes the risks arising from legionella. This article will build on previous CPD articles including modules 94 and 87 and draw on recent publications to examine some of the challenges of combating increasing risks from legionella, with examples of mediation methods relating to wholesome hot water (or domestic hot water (DHW)). As discussed in CIBSEs comprehensive guide TM13,1 many people are exposed to legionella , but their bodies defence systems respond to prevent illness. Although previously healthy people may develop Legionnaires disease (LD), there are several factors that have been shown to increase an individuals susceptibility, including: increasing age; being male; being a smoker; having an existing respiratory disease; and pre-existing illness, such as cancer, diabetes, kidney disease or alcoholism. In a particularly prescient review paper published in 2019, Bradley2 et al note that lower respiratory infections remain one of the top global causes of death and the emergence of new diseases continues to be a concern. In the rst two decades of the 21st century, we have borne witness to the emergence of newly recognised coronaviruses that have rapidly spread around the globe. Although we perhaps most frequently think of viruses when discussing emerging respiratory infections, bacteria have not been left out of the mix, as we have witnessed an increase in the number of infections from Legionella. European data reported3 by Cunha et al suggests that LD is substantially under-diagnosed and under-reported. Comparing 2011 data of reported LD from the European Legionnaires Disease Surveillance Network with that of a German multicentre study that employed active testing across a population indicates that possibly fewer than 5% of cases are being reported. If extrapolated, this would infer based on 2018 EU data4 that, rather than the 20 reports of LD per million Europeans, there could be more than 400 cases per million. In the UK, there has been a steady rise in reported cases in 2019 there were 516 confirmed cases in England and Wales5 (approximately 8.5 per million), and this is likely to be significantly fewer than actual cases. As with all potentially fatal health problems, there are associated personal tragedies, as well as significant financial consequences6,7 for the building operator if there is a failure to control the risk to occupants properly. As described by AWT,8 Legionella pneumophila was the first legionella species, named upon discovery in 1977 after the 1976 disease outbreak in Philadelphia. It was determined that neither the bacterium nor the disease was new, and that legionella bacteria have been around and causing disease for many years; it is found in the ground and groundwater. Legionella pneumophila is considered as the single species that is responsible for more than 80% of legionellosis cases. Outbreaks of LD have principally been associated with specific variations (or serotypes) collectively identified as Legionella pneumophila serogroup 1 the most common legionella in environmental samples. Legionellosis notably includes LD, a severe www.cibsejournal.com July 2020 43 CIBSE July 2020 p43-46 CPD Hamworthy 165 v2.indd 43 19/06/2020 15:59