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Tracker: See the latest levels of coronavirus in Boston-area waste water

A view of the Deer Island waste water treatment plant in Boston.David L. Ryan/Globe Staff

How much COVID-19 is circulating in the community? With the widespread availability of at-home COVID-19 tests that are not tracked by public health authorities, waste water monitoring is an important tool in assessing the the prevalence of the virus locally.

How does it work? Waste water samples are taken from the MWRA’s Deer Island sewage treatment plant and tested for traces of the coronavirus. The results, expressed as the number of SARS-CoV-2 RNA copies per milliliter of waste water, are reported publicly and tracked over time. Given that increases of coronavirus in waste water often appear ahead of case count and hospitalization increases, the system acts as something of an early warning.


Below, see the latest data from the Massachusetts Water Resources Authority.

Christina Prignano can be reached at Follow her @cprignano. Daigo Fujiwara can be reached at Follow him @DaigoFuji.