Abstract

Since micro-organisms and therefore also human pathogens in recreational waters are highly influenced by climate and environmental conditions, any climate change may alter the infectious disease burden from exposure to pathogens transmitted through recreational water. This is due to die-off or inactivation of the pathogens or, alternatively, their survival and growth. Known recreational waterborne pathogens were systematically reviewed with respect to their specific climate dependencies, water type preferences (i.e. fresh, marine or swimming pool water) and their significance to public health. Some indigenous species of bacteria, amoebas and algae are able to grow in aquatic environments, whereas enteric bacteria, viruses and parasites that are derived from human or animal faeces are not. The growth of waterborne pathogens in aquatic environments depends on environmental conditions (including climate), and on pathogen characteristics. Major climate factors that determine the number, type, virulence and infectivity of pathogens in recreational waters, and thus may have an impact on diseases transmitted through recreational water, include temperature, UV radiation, precipitation patterns and water availability. For example, increased water temperature can influence growth and die-off or inactivation of waterborne pathogens. For those pathogens that can grow in natural and artificial recreational water environments, such as Vibrio spp. in sea water, Pseudomonas aeruginosa in freshwater and Legionella in swimming pool systems, an increase in exposure and possibly disease incidence can be expected. Increased UV radiation may result in increased inactivation of enteric pathogens, or alternatively growth, whereas increased precipitation intensity will lead to peak concentrations of these pathogens due to e.g. sewage overflow and runoff. Disease that is specifically related to indoor pools is unlikely to be affected by climate factors due to the controlled environment in these facilities. With respect to the impact of climate change, there is a need to identify emerging waterborne infectious diseases and prioritise both emerging and known waterborne infectious diseases in general and recreational waterborne infectious diseases in particular. Because of the direct influence of climate on recreational water quality and the direct exposure of humans to recreational water, quantification of the impact of climate change on the disease burden through exposure to recreational water is required. Climate factors not only affect pathogen behaviour, but also influence human behaviour, thus stressing the need to study both the complexity of pathogen behaviour in recreational waters and social behaviour with respect to expected climate changes.