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By 2025, over two billion people will live in low-income urban communities with inadequate water, sanitation, and hygiene (WASH) services.

These conditions increase the risk of diseases spread through soil, water, or infected animals. The public health burden of these diseases is expected to rise with global urbanization and climate change. However, little is known about how inadequate WASH systems contribute to disease transmission or how hygiene interventions can prevent infections.

This research aims to examine how sanitation improvements, particularly through sewerage systems, can reduce disease transmission. The study focuses on three pathogens—Leptospira spp., Toxoplasma gondii, and Helicobacter pylori—which are transmitted to humans from the environment or animals. The project is evaluating the impact of improved sewerage systems on disease transmission in Salvador, Brazil, and identifying areas with concentrated disease risks.

Baseline data has been collected from 1,791 participants across six study areas (three intervention and three control). Initial findings show a seroprevalence of 8.9% for Leptospira, which causes leptospirosis, and 54% for Toxoplasma gondii, linked to serious health risks for newborns and mental health issues. These findings suggest high transmission rates in the study areas.

Environmental samples have been collected and are being tested for pathogens. The data will be linked to cohort participants using GIS technology to understand exposure to these pathogens in the community and identify behaviors that increase risk. The study will also explore how environmental factors, such as rainfall and flooding, influence pathogen spread and whether improved sewerage systems can reduce the public health burden of these diseases in urban, marginalized communities.

The findings will provide new knowledge on the role of inadequate WASH systems in disease transmission and generate evidence to inform better sanitation interventions. Results will be shared through academic articles, workshops, blog posts, and community-created videos and infographics.