Quantitative model parameters.

Uncontained fecal wastes in cities may present exposure risks to the public. We collected discarded feces from public spaces in San Francisco, CA for analysis by RT-qPCR for a range of enteric pathogens. Out of 59 samples, we found 12 (20%) were of human origin and 47 (80%) were non-human; 30 of 59 stools were positive for ≥1 of the 35 pathogens assessed, including pathogenic E. coli, Shigella, norovirus, Cryptosporidium, and Trichuris. Using quantitative enteric pathogen estimates and data on observed fecal waste from a public reporting system, we modeled pathogens removed from the environment attributable to a recently implemented program of public toilet construction. We estimated that each new public toilet reduced the annual number of enteric pathogens released into the immediate environment (within 500 m walking distance), including 6.3 x 1012 enteropathogenic E. coli (95% CI: 4.0 x 1012–7.9 x 1012), 3.2 x 1011 enteroaggregative E. coli (95% CI: 1.3 x 1011–6.3 x 1011), and 3.2 x 108 Shigella (6.3 x 107–2.5 x 109). Improving access to public sanitation can reduce enteric pathogen hazards in cities. Interventions must also consider the hygienic disposal of animal waste to reduce microbial hazards with zoonotic infection potential.