Water-Borne Infectious Disease Outbreaks Associated with Water Scarcity and Rainfall Events

Abstract

An important number of major infectious diseases are related to water. The greatest consequences for the human population are the faecal-oral water-borne infectious diseases, which are transmitted by ingestion of the causal agents that are released into water through faeces. The occurrence of outbreaks of water-borne infectious diseases could be affected by water scarcity at different degrees depend- ing on the level of water scarcity, density of population, degree of economical development, presence in the area of wild and farmed animals, etc. Still, at least in developed countries the laws and regulatory programmes regarding water quality cope with most of the problems and generally protect the population, even when scarcity obliges use of non-conventional water resources. Weather conditions influence the fate of a key factor for predicting risks and taking measures to minimize them. Unfortu- nately in many developing countries, the quality of water for consumption is still very poor independently of whether there is scarcity or abundance of water. pathogens in the water environment. Indeed rainfall favours their dissemination, and natural stressors – such as temperature and solar irradiation among others – determine their persistence. At present, heavy rain events rather than water scarcity are the main cause of failure of protective measures in devel- oped countries. This situation is likely due to an increased dissemination of the pathogens that have survived the deleterious effects of natural stressors. Higher frequency of drought followed by heavy rains, as forecasted in Mediterranean climate areas, will likely increase deficiencies in watershed protection, infrastruc- ture and storm drainage. Consequently, the risk of contamination events of the water resources will be greater than before. This combination of factors might also increase the failures in the drinking water treatments, and subsequently the occur- rence of water-borne infectious disease outbreaks. A better knowledge about the origin, survival and transport of water-borne pathogens in the water environment is