How can unsafe drinking water contribute to diarrheal disease?

Unsafe drinking water is a primary driver of diarrheal disease, largely due to the transmission of pathogenic microorganisms through the fecal-oral route. When a water supply system is contaminated by human feces, it can introduce harmful bacteria, such as Vibrio cholerae or Shigella, and protozoans like Entamoeba histolytica into the water consumed by individuals.123

Once ingested, these pathogens infect the intestine. For example, the cholera toxin disrupts the intestinal lining's ability to regulate water and electrolyte movement, causing the body to lose massive amounts of fluid, which manifests as severe watery diarrhea. Similarly, other infections like dysentery cause intestinal inflammation, leading to diarrhea that may contain blood or mucus.123

The lack of sanitary drinking water is a critical public health issue, contributing to billions of cases of diarrhea annually. Because these pathogens thrive in environments with inadequate sanitation, preventing the spread of waterborne disease requires effective water treatment processes, such as disinfection, to destroy these dangerous microorganisms before consumption.456