Sewage detects tuberculosis and pertussis outbreaks

Respiratory infections from bacteria such as Mycobacterium tuberculosis and Bordetella pertussis have risen since the COVID-19 pandemic, yet doctors and public health systems often miss or report these cases late. Clinical surveillance suffers from underreporting and delayed diagnoses, leaving gaps in our picture of where and when outbreaks occur. Wastewater monitoring — testing sewage for traces of pathogens — has proven valuable for tracking viruses and some other microbes, but it has rarely been applied to respiratory bacterial pathogens. That is surprising because bacteria can be shed in ways that send their genetic material into wastewater. In this study led by Marlene K. Wolfe, researchers set out to test whether wastewater could help detect and track tuberculosis and pertussis. They used two case studies, looking back at sewage samples collected over time from communities both with and without known outbreaks. By measuring concentrations of pathogen nucleic acids in these longitudinal wastewater samples, the team explored whether sewage signals aligned with clinical outbreaks and whether wastewater could fill important surveillance gaps.

To search for pertussis, the team designed and validated a novel B. pertussis–specific assay targeting the NAD(P) gene, then applied it to the stored wastewater samples from the case study communities. Using that new assay, B. pertussis nucleic acids were detected sporadically in wastewater during an identified outbreak, showing that the pathogen’s genetic material can appear in community sewage. For tuberculosis, the researchers used a highly specific, established assay for M. tuberculosis nucleic acids and measured low concentrations of that marker in wastewater. Importantly, the M. tuberculosis signal in sewage was lag-correlated with clinical incidence rates 5 weeks later, indicating that increases in the wastewater marker preceded reported clinical cases by about five weeks. Across both case studies the team measured concentrations retrospectively from samples collected longitudinally in communities with and without known outbreaks to compare patterns over time.

The findings support the potential of wastewater monitoring to identify communities with outbreaks of tuberculosis and pertussis and to provide an early warning for tuberculosis. Detecting low but rising levels of M. tuberculosis nucleic acids in sewage before clinical incidence increased suggests wastewater could give public health officials advance notice to investigate and respond. The sporadic detection of Bordetella pertussis during an outbreak shows promise but also indicates that signals for pertussis in sewage may be less consistent or require further refinement of methods. Because clinical surveillance alone can miss cases or report them late, adding wastewater data could help fill gaps, make outbreak detection timelier, and guide where to focus testing and interventions. These results are an initial demonstration; broader and prospective monitoring would be needed to determine how reliably sewage can track these bacterial respiratory diseases across different places and outbreak sizes.