A new study warns that climate change could undermine decades of global progress in reducing waterborne diseases, which cause nearly 1.2 million deaths from infectious diarrhea each year. More frequent extreme weather events and rising global temperatures are altering how pathogens spread and infect people, according to a comprehensive review published recently in Nature Reviews Microbiology. Researchers found climate change is modifying conditions for waterborne disease transmission around the world.[m+1]
Extreme Weather Fuels Disease Spread
Climate change drives increases in heavy rainfall, severe droughts, and warmer temperatures, all of which create favorable conditions for waterborne pathogens. Heavy rainfall and widespread flooding mobilize pathogens, contaminate clean water supplies, and overwhelm sanitation systems, releasing sewage into the environment. This direct contamination poses a significant public health risk.[pmc+7]
Droughts also increase disease risk, even though they represent the opposite end of the precipitation spectrum. When water becomes scarce, pathogens concentrate in limited water sources. People often resort to unsafe water, which increases their exposure to bacteria and other microbes.[pmc+10]
Rising temperatures directly impact pathogen survival, replication, and virulence. Warmer water can accelerate the growth of many waterborne bacteria and protozoans, making them more prevalent and dangerous. This creates a "heads I win, tails you lose" dynamic for waterborne disease, where both too much and too little water, alongside higher temperatures, increase risk.[pmc+10]
Different Pathogens, Different Threats
Climate change affects various disease-causing microorganisms, known as pathogens, in different ways. Bacteria like Vibrio cholerae (cholera) and Salmonella enterica serovar Typhi (typhoid) generally thrive in warmer conditions. Vibrio spp. infections have increased more than eight-fold in the last 40 years, often linked to increased exposure to brackish water from flooding.[m+6]
Typhoid fever, which causes over 100,000 deaths annually, sees accelerated prevalence due to climate change. A one-degree Celsius increase in mean weekly minimum temperature can lead to a 5.8 percent rise in weekly typhoid cases. Flooding increases the risk of typhoid infection by 1.76 times. Heatwaves and droughts also contribute to typhoid spread as people consume unsafe water.[ovid+5]
Parasitic protozoans like Cryptosporidium parvum also show climate sensitivity. Cryptosporidium causes severe diarrhea and is the second most common cause of diarrhea-related deaths among children younger than five. It spreads during heavy rainfall, but transmission can decrease in warmer weather in some areas. However, a study projected that by 2055, Cryptosporidium rates among children could decrease by 16.93 percent in Siaya County, Kenya, and 4.34 percent in Bamako, Mali, but increase by 24.81 percent in Basse, The Gambia, due to varying precipitation patterns.[cidrap+4]
Conversely, some viruses, including norovirus, rotavirus, and adenovirus, may spread more easily under cooler, drier conditions. This highlights the complex and varied impacts climate change has on different waterborne pathogens.[m+1]
Vulnerable Populations Face Heightened Risks
The health impacts of climate change threaten to undo the gains made in public health and development over the past half-century. Children under five, especially those in low- and middle-income countries, bear the heaviest burden of waterborne diseases. Diarrheal diseases are the second leading cause of death in this age group globally.[pmc+19]
Every day, more than 1,000 children under five die from diseases linked to inadequate water, sanitation, and hygiene (WASH). Around 1 in 3 children, or 450 million, live in areas exposed to high or very high water scarcity. These regions often have weak health infrastructure, making them least able to cope with increased disease risks without assistance.[unicefusa+5]
Dr. Elizabeth Carlton, a professor and chair at the Department of Environmental and Occupational Health at the Colorado School of Public Health, noted that climate change is "making it harder to control some of the world's most deadly infectious diseases by creating more favorable conditions for transmission."She added that climate change is "changing the rules of how these diseases spread."[news+1]
Recent cholera outbreaks demonstrate this vulnerability. In Sudan, an outbreak in September 2023 led to over 8,000 suspected cases and more than 200 deaths in just three months, as floods displaced thousands and contaminated water supplies. Malawi experienced its biggest cholera outbreak in history by February 2023, with 36,943 cases and 1,210 deaths, exacerbated by a combination of events. In Ethiopia's Somali Region, a prolonged drought triggered a cholera outbreak, resulting in nearly 800 confirmed cases and 23 deaths within two weeks, with children accounting for about 80 percent of cases.[choleraalliance+2]
Adapting to a Changing Climate
Public health responses must adapt to these evolving threats. Experts emphasize the need for tailored strategies, recognizing that bacteria, viruses, and parasites respond differently to changing environmental conditions.[m+1]
Investing in resilient water, sanitation, and hygiene (WASH) infrastructure is crucial. This includes improving access to safe drinking water and sanitation facilities, especially in vulnerable communities. The World Health Organization (WHO) projects an additional 250,000 yearly deaths by the 2030s due to climate change impacts on diseases like diarrhea, highlighting the urgency of action.[pmc+11]
Dr. Sanjay Wijesekera, UNICEF Director of Programs, stated, "Africa is facing a water catastrophe."He stressed that while climate and water-related shocks are escalating globally, "nowhere else in the world do the risks compound as severely for children."[unicefusa+1]
Deploying weather surveillance systems as early-warning tools for outbreaks can help anticipate and prevent future disease surges. Typhoid conjugate vaccines (TCVs) also offer protection in high-risk areas and after extreme weather events. Integrating climate adaptation with public health strategies is essential to protect communities and preserve the significant progress made in reducing waterborne diseases.[choleraalliance+2]
