Editing IPCC:AR6/WGII/Chapter-16 (section)

==== 16.2.3.6 Waterborne Diseases ====

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Infectious diseases with water-associated transmission pathways constitute a large burden of disease globally. Since the AR5, the evidence has strengthened that waterborne diseases, and especially gastrointestinal infections, are highly to moderately sensitive to weather variability ( ''medium confidence'' , see ‘Water distribution—Waterborne diseases’, Table SM16.23). Increased temperature and high precipitation, with associated flooding events, have been shown to generally increase the risk of diarrhoeal diseases. There are, however, a number of studies that describe important exceptions and modifications to this general observation. While high temperatures favour bacterial diarrhoeal diseases, virally transmitted diarrhoea is on the contrary mostly associated with low temperatures ( [[#Carlton--2016|Carlton et al., 2016]] ; [[#Chua--2021|Chua et al., 2021]] ). Socioeconomic determinants, such as the existence of single-household water supplies ( [[#Herrador--2015|Herrador et al., 2015]] ) or combined sewer overflows ( [[#Jagai--2017|Jagai et al., 2017]] ), have been shown to critically increase the risk of gastrointestinal infections linked to heavy rainfall in high-income countries. Also, for both low- and high-income countries it has been found that gastrointestinal diseases increase following a heavy rainfall event only if preceded by a dry period ( [[#Carlton--2014|Carlton et al., 2014]] ; [[#Setty--2018|Setty et al., 2018]] ). Yet, so far there is no consistent evidence on the role of droughts in favouring waterborne disease transmission ( [[#Levy--2016|Levy et al., 2016]] ). As exemplified by the large cholera outbreak following the 2010 earthquake in Haiti, the existence of functioning sanitation systems is critical for preventing waterborne disease outbreaks, while climatic factors (especially rainfall) are important in driving the transmission dynamics once the outbreak has started ( [[#Rinaldo--2012|Rinaldo et al., 2012]] ). Other socioeconomic factors, such as human mobility and water management projects (e.g., dam constructions), also modify the strength of the association between climatic factors and waterborne diseases, as shown by recent studies in Africa ( [[#Perez-Saez--2015|Perez-Saez et al., 2015]] ; [[#Finger--2016|Finger et al., 2016]] ).

Whereas the weather sensitivity of waterborne diseases is well established for all world regions (see ‘Water distribution—Water-borne diseases’, Table SM16.23), studies attempting to attribute recent trends in waterborne disease to climate change are non-existent, except for investigations on the distribution of marine ''Vibrio'' bacteria and associated disease outbreaks in the coastal North Atlantic and the Baltic Sea regions ( [[#Baker-Austin--2013|Baker-Austin et al., 2013]] ; Baker- [[#Austin--2016|Austin et al., 2016]] ; [[#Vezzulli--2016|Vezzulli et al., 2016]] ; [[#Ebi--2017|Ebi et al., 2017]] ). These investigations provide evidence that increases in sea surface temperatures over recent decades as well as during recent summer heatwaves are linked to increased concentrations of ''Vibrio'' bacteria in coastal waters and an associated rise in environmentally acquired ''Vibrio'' infections in humans.

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