Boston Wastewater Monitoring

Wastewater contains valuable public health information. People who are ill with 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 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, which are presented on the BPHC Respiratory Illness Dashboard. 

BPHC partners with Biobot Analytics, a company based in Cambridge, MA, to measure the amount of SARS-CoV-2, RSV, and influenza A and B viruses in each wastewater sample. Biobot uses a polymerase chain reaction (PCR) test to measure the concentration of each of the viruses, and we report 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. Results are updated twice per week, and 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 viruses that cause the 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 COVID-19, the flu, and RSV. We have compiled these resources so they correspond with each of the wastewater risk levels. 

Find these resources here: Public Health Recommendations by Wastewater COVID-19 Level

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.

Read the document

BPHC’s ability to gather and share data about the number of COVID-19 infections has decreased as fewer tests are reported. While not able to provide an exact number of infected people, wastewater data indicate 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 means we need a better view of how local communities are affected. Wastewater has proven useful during the pandemic for anticipating trends in 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 COVID-19 often begin shedding virus in stool before developing symptoms, wastewater serves as an early indicator of COVID-19 cases. Wastewater data need to be considered along other public health indicators, like the number of COVID cases or hospitalizations, to truly understand the public health impact and risk of COVID-19. These can be seen together on the BPHC Respiratory Illness Dashboard. 

Samples are collected twice weekly from 12 sewerholes in 11 neighborhoods throughout the city. The collected sewage is sent to Biobot’s laboratories in Cambridge. Biobot uses qPCR, similar to the nasal swab tests clinics use to test people for COVID-19. A process called genomic sequencing is also performed to determine which variants of SARS-CoV-2 are present. For influenza A, influenza B, and RSV, the process is similar, except Biobot quantifies these with a technology called digital PCR (dPCR) instead. 

The wastewater risk level reflects the amount of SARS-CoV-2 present in the wastewater sample. A higher risk level indicates a higher amount of virus is present in recent samples. 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 trend indicates how the amount of virus in wastewater is changing over time. An increasing trend means the amount of virus in the sewage in is increasing, suggesting more people are becoming infected with SARS-CoV-2 and are shedding it into the sewer. A decreasing trend means the amount of virus in the sewage is decreasing, suggesting fewer people are becoming infected with SARS-CoV-2. 

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. 

For more information, see Biobot’s description of their process for identifying variants of the virus. 

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.