This study utilizes secondary data analysis to characterize the relationship between enteric infections, population density and sanitation coverage in Guatemala. Researchers at the University of California at Berkeley combined two separate datasets to characterize and compare sanitation coverage, enteric infection rates and population densities in Nueva Santa Rosa, Guatemala. Working with their partners at Universidad del Valle researchers sought to better understand the characteristics and risk factors associated with enteric infection and WASH coverage in the study area.
Guatemala: Nueva Santa Rosa
To explore the relationship between population density and sanitation, University of California, Berkeley analyzed individual and household level data from Guatemala. This study is a desk review of two datasets collected in Nueva Santa Rosa, Guatemala. Researchers classified each household based on sanitation conditions and population density at the household level. Population density was measured through the estimation of the number of people within a 50m radius of a household, followed by the classification of “high” or “low” density areas based on aerial images of a subset of these houses. A cut point for “high” density that maximized researcher agreement was then estimated. The study team then used these and other measures in the datasets to estimate the relationship between population density, sanitation and health outcomes.
POPULATION DENSITY & ENTERIC INFECTIONS
Researchers found overall diarrhea prevalence was lower in high density areas but the rates of infection with rotavirus and shigella, diarrhea causing pathogens, were higher in high population density areas. Rotavirus and Shigella may be transmitted primarily person-to-person and this may explain the discrepancy.
POOR SANITATION & ENTERIC INFECTIONS
Researchers found differences in enteric infections, with generally higher rates of infection presenting in households with poor sanitation. Initially results showed an increased prevalence of Ascaris infection, 3.5 times higher, in high density households with poor sanitation however when adjusted for confounding variables the associations disappeared. In an exploratory analysis of the Ascaris results researchers discovered looked at spatial components of transmission pathways.
SOURCES OF CONFOUNDING
Evidence from this study shows the single largest source of confounding is a composite wealth index. Researchers found the lowest quintiles of wealth to be at greatest risk for certain infections. They hypothesize there are proximal factors accounting for this difference such as access to deworming medicine or living in a household with a dirt floor which increases the odds of infection with soil-transmitted helminths.
These findings indicate that in the Guatemalan context poor sanitation poses little difference in infection prevalence or risk of enteric infection between high and low population density areas. However evidence of the relationship between high density, poor sanitation and poverty and helminth transmission points to the persistence of STH infection in the lowest wealth quintiles.
A peer-reviewed paper on the full findings is forthcoming. This paper will be targeted towards policy makers and donors in order to make the best use of limited resources. Researchers are also collaborating with authors of the second desk review to publish a joint paper on study methods.