Boston Wastewater Monitoring

Wastewater contains valuable public health information.  People who are ill with diseases like COVID-19, the flu, or RSV can shed viruses into Boston’s sewer network when they use the bathroom. People with these illnesses may begin shedding viruses into the sewer even before noticing any symptoms of the infection. By measuring the amount of certain viruses in wastewater, we can observe the level of these illnesses in each neighborhood over time. This information can provide additional context to other public health indicators for these diseases, like those presented on the BPHC Respiratory Illness Dashboard.  

BPHC partners with GT Molecular, a company based in Colorado, to test wastewater samples for viruses such as SARS-CoV-2, RSV, measles, and influenza A and B, and to measure how much of each virus is present. GT Molecular then uses a polymerase chain reaction (PCR) test to measure the concentration of each of the viruses, and BPHC reports a smoothed value to observe trends in these concentrations over time for each neighborhood.

By comparing the first year of SARS-CoV-2 wastewater data to COVID-19 cases and hospitalizations, BPHC determined thresholds that reflect different levels of risk of COVID-19 outcomes. BPHC categorizes each result according to two factors: the wastewater risk level, which corresponds to the amount of infections in that neighborhood, and the wastewater trend, which indicates whether there is more or less virus in the wastewater compared to two weeks ago.

BPHC also began testing for other viruses like flu and RSV in October 2023. BPHC is working on developing similar tools to assist in interpreting data for these viruses.  

For more information, please read the Frequently Asked Questions below, or email wastewater@bphc.org with questions.  

BPHC and the US CDC provide recommendations to prepare for and prevent viruses like COVID-19, the flu, and RSV. We have compiled these resources so they correspond with each of the wastewater risk levels.

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To learn more about the statistical methods used to determine the wastewater levels and trends presented on this site, please read the Technical Document below. This document describes the methods for creating interpretable and actionable description of neighborhood-level COVID-19 wastewater levels and trends for routine reporting. 

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Wastewater surveillance acts as an early warning system, because it captures presence of a virus in sewage systems even before infected individuals may be symptomatic or diagnosed.  This early alert helps us inform other public health agencies, trigger response actions, and identify where diseases may be spreading before official diagnosed cases are reported by traditional clinical case systems.

For example, BPHC’s ability to gather and share data about the number of COVID-19 infections decreased as at-home tests became more accessible and fewer clinical test results were reported. While not able to provide an exact number of infected people, wastewater data provides an alternative data source to track the relative level of disease spreading in a community and fill this gap in our data.  

The disproportionate impact of the pandemic on vulnerable communities in Boston also illustrated that we need a better understanding of how specific communities are affected. Wastewater has proven useful during the pandemic for anticipating localized trends among diseases like COVID-19.  

Wastewater data are community-level, anonymous, rapid, non-invasive, and do not rely on people having access to or seeking healthcare in order to know people are infected. Because people with diseases like COVID-19 often begin shedding virus in stool before developing symptoms, wastewater serves as an early indicator of cases. Wastewater data need to be considered along with other public health indicators, like the number of cases or hospitalizations, to truly understand the public health impact and risk of emerging infectious disease trends, like those seen together on the BPHC Respiratory Illness Dashboard.  

Samples are collected twice weekly from 11 sewerholes in 10 neighborhoods throughout the city. The collected sewage is sent to GT Molecular's laboratories in Colorado. GT Molecular uses PCR, similar to the nasal swab tests clinics use to test people for COVID-19, to measure the amount of virus present in the wastewater.

The wastewater risk level reflects the amount of a virus present in the wastewater sample. A higher risk level indicates a higher amount of virus is present in recent samples.

For example, BPHC compared the first year of SARS-CoV-2 wastewater data to other COVID-19 indicators, and found that high levels of SARS-CoV-2 in wastewater correspond to high levels of COVID-19 outcomes, such as reported cases and hospitalizations.

The wastewater risk level reflects the amount of virus present in the wastewater sample. A higher risk level indicates a higher amount of virus is present in recent samples.

For example, BPHC compared the first year of SARS-CoV-2 wastewater data to other COVID-19 indicators, and found that high levels of SARS-CoV-2 in wastewater correspond to high levels of COVID-19 outcomes, such as reported cases and hospitalizations.

Sites were selected with the goal of reaching as many of Boston’s neighborhoods as possible in order to have a representative snapshot of COVID transmission in the city. A citywide wastewater signal is calculated by taking a population-weighted average across these different sites. 

Wastewater data is similar to other public health indicators we have used throughout the pandemic to understand risk and make adjustments, such as test positivity and hospitalizations. Just as you would check your weather app to see if you need an umbrella to prevent yourself from getting rained on, checking wastewater data can be used to decide when to take more precautions to prevent infection. We have compiled guidance from BPHC and the US CDC for what actions you can take to prevent infection based on the wastewater level. 

Samples are collected twice weekly and this page is updated when data become available. 

Our network of sites will not include every person in Boston. These are meant to offer a snapshot across different areas of Boston to capture a citywide perspective. Everyone in Boston participates in wastewater surveillance, either through the BPHC program or through the MADPH surveillance of the Deer Island Treatment Plant, which collects wastewater from Boston and its surrounding suburbs. 

BPHC has developed a wastewater program to monitor disease trends within the city of Boston. Other sources of wastewater data, including data from the Deer Island Treatment Plant that treats wastewater from the Greater Boston Area, include contributions from surrounding communities, which can lead to different results. Other reasons these results may differ include: recent results may not be available, the laboratory that tests wastewater for BPHC may use different methods than laboratories testing wastewater for other organizations, and other organizations may use different methods to describe trends in their data.

In short, what BPHC publishes here is its best understanding of data from the BPHC Wastewater Monitoring Program. BPHC is not involved in producing or interpreting wastewater-related data coming from other sources.