Significance: Diseases related to poor or lack of access to clean water, sanitation, and hygiene negatively impact health, education, and development worldwide and cause millions of deaths in children each year. Health outcomes associated with lack of access to clean water and sanitation are under-evaluated.

Aim: To assess the effect of improved water and sanitation infrastructure development on child morbidity in Peru by investigating diarrhea in children under five years of age.

Methods: The child, family, and household data from the Peruvian Demographic and Health Surveys (DHS) were used to evaluate the association between access to water and sanitation and diarrhea in children under five using logistic regression analysis.

Results: This study found an association between under five years of age diarrhea and improved sanitation access, current age of child, and the interaction between drinking water access and natural region. Safe disposal of child’s stool appeared to be protective against diarrhea, but was not statistically significant (OR= 0.87, p= 0.0642). Improved sanitation was protective (OR= 0.85), being younger increased risk of diarrhea with those 6-11 and 12-23 months with highest odds (OR= 2.56; OR= 3.47), and those living in the Rainforest with improved and unimproved water access had increased risk of diarrhea (OR= 1.78; OR= 2.62).

Conclusion: Natural region is the primary factor predicting diarrhea risk, as well as type of drinking water, specifically for those living in the rainforest natural region. The rainforest region of Peru has the highest rates of diarrhea and the highest proportion of poor people. As with many diseases, further research of Peruvian regions and states suggest that multifactorial causes of diarrheal diseases could be at play.