(August 2007) Water and sanitation play a crucial role in the transmission of diarrheal disease. These environmental factors contribute to approximately 94 percent of the 4 billion cases of diarrhea that the World Health Organization (WHO) estimates to occur globally each year. Children under the age of 5 in developing countries bear the greatest burden and account for the majority of the 1.5 million deaths attributed to diarrhea annually.1 In Latin America and the Caribbean (LAC), roughly 77,600 children under the age of 5, over 200 children every day, die each year from diarrhea and its complications.2 Although 16 of the 33 countries in the LAC region are on track to meet the United Nations' Millennium Development Goals (MDGs) for sanitation and clean water, countries in LAC still need to extend water and sanitation access to an additional 6.1 million and 8.4 million people, respectively, to fully meet the MDG targets.3 The impact of climatologic fluctuations on water quality and supply must be examined to ensure continued reduction in diarrheal diseases.

Water and Sanitation and Their Effects on Diarrheal Illnesses

Diarrhea can cause severe dehydration and poor absorption of nutrients, which in turn make affected individuals more susceptible to infectious diseases. Diarrhea in early childhood is associated with impaired growth, physical fitness, and cognitive development, which can lead to diminished future school performance and lower economic earning power.4 Severe diarrhea that is not cared for appropriately can also lead to death. Safe drinking water and improved sanitation play a significant role in reducing the risk of diarrheal diseases.

Although the LAC region is close to meeting the MDGs concerning water and sanitation, LAC's population of 554 million still includes 50 million people who lack access to safe drinking water—34 million of whom reside in rural areas—and 125 million people who lack access to improved sanitation.5 Unimproved water sources are vulnerable to contamination and are a major source of disease transmission; unimproved sanitation is a major source of contamination for clean water sources. According to WHO, diarrhea morbidity could decrease by 32 percent with improved sanitation such as pit latrines, septic tanks, and composting toilets; and by 6 percent to 25 percent with improved water supply such as protected dug wells, public taps, and tube wells.6

Climate Change and Its Effects on Diarrheal Illnesses

Climate encompasses the weather patterns in a geographic area over long periods of time, typically measured in years, whereas weather consists of the fluctuations in the atmosphere, like temperature, precipitation, and wind, over a period of hours or days. LAC has several different climate zones that increase its overall vulnerability to climatological natural disasters. From 1970 to 1999, over 70 percent of the disasters in LAC were meteorological in origin, with floods being the most important disaster-causing phenomenon.7

Compounding the potential effects of this meteorological vulnerability, the highest concentration of population in LAC is along the coasts: approximately 60 percent of the region's people reside in coastal states or provinces, and 60 of the region's 77 largest cities are situated along the coast. Between 1970 and 1999, 30 natural disasters in LAC involved hurricanes, floods, droughts, or tsunamis, all of which potentially contribute to increases in waterborne illnesses from their varied effects.8 Jonathan Patz’s conjecture that "human impacts occur when climate hazards and population vulnerability converge" helps explain why LAC is so vulnerable to climate-related health effects.9 Furthermore, increased weather extremes are one consequence forecasted to follow from climate changes predicted by the Intergovernmental Panel on Climate Change.10

In addition, the creation of safe water sources and effective sanitation systems does not guarantee protection from contamination or destruction from natural disasters. UNICEF calculated that in LAC "between 1994 and 2003 the economic losses in water and sanitation were about $650 million, as a result of at least 2,100 urban systems damaged, 4,500 rural aqueducts affected, and 28,000 wells and 173,000 latrines destroyed" due to natural disasters including floods, hurricanes, and earthquakes.11 These figures illustrate the impact of natural disasters on established water systems. Extend these figures to include the impact on unimproved water and sanitation sources, such as a community that gets its water from surface sources, and the effects on health are even more distressing. These factors are reflected in Table 1, which displays the physical and economic damages to water and sanitation systems in LAC as a result of Hurricane Mitch in 1998.

Table 1
Summary of Damage to Water and Sanitation Systems Caused by Hurricane Mitch (October 1998)

Damage to Water and Sanitation Systems
Damages (US$)
Honduras 90% or more of population without access to water service in early November; 40% without access by late November
$58.0 million
32% of water service infrastructure damaged
$19.8 million
396 communities with damaged systems; 20,000 latrines destroyed
$16.1 million
El Salvador
32% of water service infrastructure damaged
$2.4 million

Source: Pan American Health Organization, Emergencies and Disasters in Drinking Water Supply and Sewerage Systems: Guidelines for Effective Response (Washington, DC: PAHO, 2002).

Damage from one major meteorological event can cause severe public health and financial consequences. Infrastructure that is destroyed or overburdened during natural disasters leads to human health consequences. Two specific weather extremes in LAC will be explored below—El Niño and temperature change. Although it will not be discussed extensively here, drought also has an impact on human health.

El Niño and Severe Rainfall/Flooding

While El Niño (El Niño/Southern Oscillation) is a natural climate fluctuation, usually occurring every three to seven years, there is concern that climate change will increase its frequency or the severity of its consequences. El Niño is characterized by an increase in high atmospheric pressure in the southeastern Pacific, coupled with low pressure over the Indian Ocean, which results in the namesake oscillation of wind and ocean currents. These, in turn, change regional temperatures and precipitation patterns and lead to significantly increased rainfall.12

Several researchers have established a link between heavy rainfall and flooding—whether resulting from El Niño-associated events or from other meteorological impacts—and subsequent outbreaks of infectious diseases.13 Extreme meteorological events can easily disrupt water purification and storm water and sewage systems, as well as contaminate uncovered wells and surface water, leading to an increased risk of illness.14 These risks are even higher when a population lives in a low-lying area, where the land’s hydrology causes draining tributaries to meet.15 Conversely, heavy rains and coastal events can also flush microorganisms into watersheds, affecting those up-coast as well.16 Nonsustainable development, such as that which contributes to deforestation and soil erosion, influences water contamination by destroying the land's natural ability to absorb runoff, resulting in water-contaminating mudslides.

The 1997-1998 El Niño caused severe flooding in Peru, Ecuador, Argentina, and Uruguay, where daily rainfall totals topped 7.5 to 12.5 cm.17 Coupled with the ambient and ocean temperature changes that an El Niño can produce, negative effects on diarrheal disease incidence have been recorded. During the 1997-1998 season, one analysis showed an increase of over 200 percent in hospital admissions for childhood diarrhea over expected trend data from the previous five years.18 In terms of weather-illness correlation, research has shown that "for each degree centigrade of increase in mean ambient temperature, the number of admissions increased by 8%."19 In the South Pacific, there has been a "positive association between the annual average temperature and the rate of diarrhea."20

In a retrospective case review of cholera-like dysentery during 1990-1991, it was hypothesized that El Niño-influenced ocean warming and its associated hypergrowth of plankton contributed to the dispersal of vibrio cholerae organisms—responsible for cholera—along the Pacific coast of Peru.21 In the first year of the ensuing outbreak, more than 300,000 Peruvians became ill with cholera from ingesting contaminated water or sea life, as well as from person-to-person spread potentiated by nonexistent or poor sanitation infrastructure.22

Increased Temperatures

Climate change can result in increased temperatures in both ocean water and ambient air. Increased sea temperatures have a direct effect on the proliferation of plankton and algae in sea water. Vibrio species organisms, including v. cholerae, thrive in particular sea conditions. Among these are warm water, moderate salinity, and number of aquatic invertebrates, all conditions influenced by climate change.23 In particular, the quantity of vibrio species may increase or the range of the bacteria may extend; a combination of these circumstances may have occurred in Peru during the 1991 cholera outbreak.24

Surface water warmth also contributes to the strengthening of hurricanes. A minimum sea temperature of 26 degrees Celsius is needed for hurricanes to form, but a sea temperature of 27.8 degrees Celsius—less than 2 degrees warmer—will cause hurricanes to strengthen.25 Given the geographical vulnerability of a large portion of LAC to hurricanes, this effect of climate change is likely to contribute to more devastating consequences from these tropical storms.

Increased ambient air temperatures are another result of climate change, often referred to as "global warming," implying the effect of increased ambient ozone from excess emissions. Air/temperature inversions can also occur, trapping warmer air closer to the Earth's surface. Many causative agents of diarrheal disease have a seasonal variability, with peaks in the warmer months.26 Increased temperatures or higher temperatures for longer times can result in higher than expected diarrhea incidence.27

Finally, rises in sea level due to increased temperatures can lead to coastal flooding, which can force the use of contaminated water, overwhelm sanitation systems, or prompt migration into areas with insecure water and sanitation availability.


The impacts of water and sanitation on diarrheal disease—and the actions needed to minimize this impact—are well known. Less well known are the potential human health effects of climate change. Although emerging research is testing hypotheses about the likely consequences, most of this research is retrospective, assessing the impacts from past severe weather events. Our recommendations for policymakers concerned with the impacts on diarrheal diseases from meteorological changes can be divided into two categories: surveillance and monitoring, and infrastructure and development. Household interventions, while not discussed here, are also effective, and communities and governments in LAC should continue to promote at-home water storage, water treatment, and handwashing.

Among surveillance recommendations, we focus on three areas that policymakers and program planners need to address: climate-related surveillance, water quality monitoring, and diarrheal disease surveillance. Ideally, these three surveillance and monitoring activities would be planned and conducted in a multisectoral fashion, gathering input from each of the relevant and responsible sectors and creating one overarching plan for "climate and health" monitoring activities in the target area. In reality, this is difficult, and many areas may already have one or more components of the suggested surveillance underway. In those cases, the important actions would center on linking the different data sets in a way that would enable policymakers and planners to obtain timely, useful information that would benefit the design of interventions to limit the human health impact of climate change events. (One example of such an integrated system is the SERVIR project, a near real-time Mesoamerican monitoring system that combines multiple data sources to inform about climatic changes and their potential human effects. To view online, go to: http://servir.nsstc.nasa.gov/index.html.

In particular, researchers have suggested monitoring, undertaken by multiple disciplines, with the aim of detecting various large climate events (and smaller physical changes) that could indicate impending problems. For example, experts in marine biology, satellite imagery, and clinical surveillance could become a robust team for monitoring health effects from climate change. At the micro level, surveillance efforts should monitor for increased temperatures and surface height, as well as changes in sea water salinity, nutrient concentrations, and plankton blooms.28 At the macro level, monitoring for heat waves, floods, and heavy rainfalls would be beneficial because these are acknowledged precursors to potential population disease effects.29 Whether or not countries in LAC could undertake each of these specific activities remains in question. Larger countries with greater monetary and personnel resources, and those with more-developed health and science systems, may be able to achieve these goals. In those countries with fewer or less-developed resources, regional consortia could help to level capacity among countries with varied capabilities but shared risks.

Table 2 (PDF: 29KB)  more specifically describes the focus areas and potential action steps for our surveillance and monitoring recommendations. Policymakers and program planners must recognize that improved water and sanitation access cannot completely mitigate the impact associated with diarrheal diseases and water contamination, especially in the event of climate changes. Thoughtful community development and infrastructure enhancement have the potential to play a significant role in reducing diarrheal incidence. Therefore, policymakers and program developers should address sustainable development, conservation, and construction of durable water systems, and should allow community input into water system planning.

Conservation of the natural integrity of land and ecosystems, through both conservation and controlled development, provides natural protection to water and sanitation systems by making them less vulnerable to contamination. Policies to control development could also serve to avert nature hazards and their resulting effects. Deforestation—often the result of clear-cutting for development—increases the frequency of mudslides, which contaminate water systems. Additionally, "the restoration of ecosystems, particularly protection of wetlands, may also influence the occurrence and distribution of hazardous microbial blooms, as coastal wetlands filter nutrients, microorganisms and chemicals and buffer coasts from storm surges."30 With 60 percent of the population in LAC living in coastal areas, degradation of the ecosystem could devastate livelihoods and cause ill health. Therefore, policymakers must recognize the potential hazards in uncontrolled development and create water and sanitation infrastructure suitable to handle growing populations.

Further, effectively managing infrastructure development provides policymakers an opportunity to effectively design water and sanitation systems for growing communities. Planners can address potential problems during the design phase to lower the likelihood of failures and to save money. Water and sanitation systems need to be strategically designed and placed to prevent or reduce contamination or destruction during climatologic events. Disrupted services reduce any benefits the community gains from having improved systems. Not only do such disruptions reduce access to clean water and sanitation, they also increase contamination of nearby water systems and contribute to environmental degradation. For example, the Peruvian Ministry of Health, in collaboration with the Pan American Health Organization (PAHO) and WHO, calculated 199 water system failures caused by the recurrent effects of El Niño between 1997 and 1998, affecting a population of 156,000 in rural areas of Peru. The shortage of water and the poor quality of the available water resulted in a 3.2 percent increase in acute gastrointestinal illness, just in the firsts few months of El Niño.31 Strategic planning to enhance the reliability of such systems, especially in coastal areas, should be a top priority.

While improving access to hardware (wells, latrines, and sewage systems) is essential, the long-term success of these improvements depends on community participation in the decisionmaking processes, as well as continued infrastructure and program maintenance backed by political commitment. Intervention projects will not result in sustained benefit unless accompanied by: effective community involvement in determining appropriate water and sanitation systems that accommodate social norms; education about the relationship between illness, sanitation, and hygiene; and political commitment to infrastructure improvements.32 In addition, policymakers must make access to improved water and sanitation systems a priority for all populations, especially rural communities that are currently well below the relevant MDGs in water and sanitation. Policymakers should also incorporate the latest climate change science into their plans to enhance the sustainability of the systems they recommend for development. The potential impacts created by climate change need to be clearly defined prior to the development of systems to help ensure sustainability.

Further, policymakers must coordinate and ensure execution of responsibilities during an emergency by creating an emergency plan to recover disrupted services as soon as possible, while simultaneously providing alternative access to water and sanitation during system down-time. While the destruction of a water or sanitation system in the wake of a natural disaster is unfortunate, governments can use such failures as models to test and design new ideas for improved systems that might resist damage or contamination.33

Jennifer Fricas works for Seattle University. Tyler Martz is a recent graduate of The George Washington University School of Public Health. The authors would like to thank the following reviewers: Roger-Mark De Souza, Richard Skolnik, Lisa Colson, Melissa Thaxton, Heather D'Agnes, and David Goldsmith.


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  14. Charvériat, "Natural Disasters in Latin America and the Caribbean."
  15. Joan B. Rose et al., "Climate Variability and Change in the United States: Potential Impacts on Water- and Foodborne Diseases Caused by Microbiologic Agents," Environmental Health Perspectives 109, suppl. 2 (2001): 211-21.
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  17. William Checkley et al., "Effect of El Niño and Ambient Temperature on Hospital Admissions and Diarrhoeal Diseases in Peruvian Children," Lancet 355, no. 9202 (2000): 442-50.
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  19. Reena B.K. Singh et al., "The Influence of Climate Variation and Change on Diarrheal Disease in the Pacific Islands," Environmental Health Perspectives 109, no. 2 (2001): 155-59.
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  21. Checkley et al., "Effect of El Niño and Ambient Temperature on Hospital Admissions and Diarrhoeal Diseases in Peruvian Children."
  22. Erin K. Lipp et al., "Effects of Global Climate Change on Infectious Disease: the Cholera Model," Clinical Microbiology Reviews 15, no. 4 (2002): 757-70.
  23. Seas et al., "New Insights on the Emergence of Cholera in Latin America During 1991."
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  25. Patz et al., "The Effects of Changing Weather on Public Health."
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  32. PAHO, The Challenge in Disaster Reduction for the Water and Sanitation Sector.
  33. Patz et al., "The Effects of Changing Weather on Public Health."