The rapid development of megacities, and their growing connectedness across the world
is becoming a distinct driver for emerging disease outbreaks. Early detection of unusual
disease emergence and spread should therefore include such cities as part of risk-based
surveillance. A catch-all metagenomic sequencing approach of urban sewage could potentially
provide an unbiased insight into the dynamics of viral pathogens circulating in a
community irrespective of access to care, a potential which already has been proven
for the surveillance of poliovirus. Here, we present a detailed characterization of
sewage viromes from a snapshot of 81 high density urban areas across the globe, including
in-depth assessment of potential biases, as a proof of concept for catch-all viral
pathogen surveillance. We show the ability to detect a wide range of viruses and geographical
and seasonal differences for specific viral groups. Our findings offer a cross-sectional
baseline for further research in viral surveillance from urban sewage samples and
place previous studies in a global perspective.
