All coliforms are not created equal: A comparison of the effects of water source and in‐house water contamination on infantile diarrheal disease

Abstract

Storing drinking water in the home is common in the developing world. Several studies have documented increased concentrations of fecal coliforms during household storage. This has led to the belief that in‐house water contamination is an important transmission route for enteric pathogens and, moreover, that improving water source quality is not warranted until that quality can be maintained in the home. We contend that in‐house water contamination does not pose a serious risk of diarrhea because family members would likely develop some level of immunity to pathogens commonly encountered in the household environment. Even when there is no such immunity, transmission of these pathogens via stored water may be inefficient relative to other household transmission routes, such as person‐to‐person contact or food contamination. A contaminated water source poses much more of a risk since it may introduce new pathogens into the household, The effects of water source and in‐house contamination on diarrheal disease are estimated for 2355 Filipino infants. The results confirm our hypothesis: contaminated water sources pose a serious risk of diarrhea while contamination of drinking water in the home does not. Water boiling is shown to eliminate the risk of diarrhea due to water source contamination. The results imply that improvements in water source quality are more important than improving water storage practices.