Association between heavy precipitation events and waterborne outbreaks in four Nordic countries, 1992–2012

Abstract

We conducted a matched case-control study to examine the association between heavy precipitation events and waterborne outbreaks (WBOs) by linking epidemiological registries and meteorological data between 1992 and 2012 in four Nordic countries. Heavy precipitation events were defined by above average (exceedance) daily rainfall during the preceding weeks using local references. We performed conditional logistic regression using the four previous years as the controls. Among WBOs with known onset date (n = 89), exceedance rainfall on two or more days was associated with occurrence of outbreak, OR = 3.06 (95% CI 1.38-6.78), compared to zero exceedance days. Stratified analyses revealed a significant association with single household water supplies, ground water as source and for outbreaks occurring during spring and summer. These findings were reproduced in analyses including all WBOs with known outbreak month (n = 186). The vulnerability of single households to WBOs associated with heavy precipitation events should be communicated to homeowners and implemented into future policy planning to reduce the risk of waterborne illness.

Climate Change and Water-Related Infectious Diseases

“…There have been a number of previous reviews and publications highlighting potential impacts of climate change and water-related illness in water-related or waterborne disease [37,38,117,[172][173][174][175][176][177][178][179][180][181][182]. Some approaches examine the technological means to best represent the data [42,175,177,178,183], some examine outbreaks [28,32] and others focus on effects of the hydrological cycle in particular regions [28,110,174,179], while others have adopted a systematic review approach [37]. This paper has examined a full range of water-related pathogens, providing an evidence base for regarding them as water-related and indicating which studies have provided evidence.…”

“…There are many studies that have examined the role of rainfall before an outbreak. It is generally seen that heavy rain is more common before many outbreaks, suggesting the source water is compromised [32,36,[110][111][112]. The association between waterborne outbreaks with a period of prolonged low rainfall in the four weeks before an outbreak may also indicate a vulnerability to weather [32], although this was not seen in other studies.…”

“…The impact of a changing climate is most important when it comes to the quality of drinking water and diarrhoeal diseases, particularly in developing countries [37]. There are relationships between many of the bacterial infections and temperature, and evidence of links to heavy rainfall and flooding [32,110,117]. The sources of exposure may be agricultural [153] or from sewage, and the different sources contain different pathogens, with human viruses rarely being detected in animal waste [154].…”

Impact of Climate Forecasts on the Microbial Quality of a Drinking Water Source in Norway Using Hydrodynamic Modeling

“…With the imminent threat of changing climate variables on the quality of freshwater resources, water treatment plants that are heavily dependent on surface water bodies are particularly vulnerable. Microbial deterioration of surface water sources occurring during extreme precipitation events and the resulting impact on the integrity of water treatment plants and disease outbreaks have been widely investigated [5][6][7][8][9][10][11][12][13][14][15][16]. Furthermore, increasing numbers of natural organic matter in surface water sources due to changes in precipitation patterns and catchment attributes [17] may challenge the efficacy of water treatment processes, enhance regrowth of bacteria in the water distribution network, and result in waterborne disease outbreaks [18][19][20][21].…”

Climate-driven QMRA model for selected water supply systems in Norway accounting for raw water sources and treatment processes

“…In particular, water supply systems that depend on surface water sources will be the most challenged. Microbial deterioration of surface water sources due to increased precipitation have been directly linked to waterborne disease outbreaks (Curriero et al, 2001;Mann et al, 2007;Nichols et al, 2009;Cann et al, 2013;Tornevi et al, 2015;Beaudeau et al, 2014;Guzman-Herrador et al, 2016;Drayna et al, 2010). In addition, seasonality in sporadic cases of waterborne diseases may be explained by seasonal contamination of surface water bodies (Patz & Han, 2013).…”