**11. Preparing for Climate Change**

The principal reason for drinking water infections is the absence of reliable infrastructure. For rural communities worldwide, this includes the source waters used for drinking, the methods used to transport it from source to household, safe storage within the household, any treatment used and hygiene and sewage disposal changes. The principal underlying factor is poverty. Improving water treatment needs to be accompanied by improvements in sewage disposal and hygiene training. Climate change will not alter these underlying principles. What could change is the frequency of water shortages, population movements, conflict, refugee camps and so on, and a deterioration in the hygienic quality of water that people receive. Good planning associated with disasters can reduce the risks of waterborne diseases [41]. Any increase in disease associated with disasters in developing countries can have knock-on effects in developed ones.

With climate change, it is important to build knowledge of the mechanisms by which changes in weather can influence individual pathogens, and how these may subsequently affect human health. Not all problems associated with diarrhoeal diseases are as a result of outbreaks and it is important to understand the drivers for sporadic disease, and the disease burdens associated with the range of common pathogens. Good surveillance is necessary in order to detect clusters and outbreaks at an early stage, so that they can be investigated and controlled in a timely way, and so that future outbreaks can be prevented.

Most enteric pathogens are very seasonal, with bacterial pathogens (e.g., *Salmonella* spp., *Campylobacter* spp., STEC) predominating in the summer months, while viral gastroenteritis predominantly peaks in the winter (e.g., norovirus, rotavirus) [171]. The analytical examination of weather drivers has relied on time series approaches, that have limitations due to the collinearity between, for example temperature and seasonality, making it difficult to get definitive evidence of the causal mechanisms and to predict the impact of changes in climate. A review of mathematical approaches to demonstrating weather influences on waterborne infections has been undertaken [172]. The studies grouped into two clusters: Process-based models (PBM) and time series and spatial epidemiology (TS-SE). A review of analytical epidemiology studies looked at the quality of evidence

for associations with rainfall, temperature, and so on, and waterborne disease identified the difficulties with developing optimum approaches [117]. A more systematic examination of the seasonality of a full range of pathogens [171] may widen our understanding of those that are linked to climate fluctuations. There are also a range of less analytical approaches that can contribute to a better understanding of waterborne pathogens and future risks (Table A1, Appendix A). Further development of tools to separate the effects of weather from other influences on seasonality needs to be undertaken, utilising surveillance data from a wider geographic area and linking local cases to local weather.
