Massachusetts Wastewater Surveillance Dashboard — COVID-19, Influenza, and RSV

Published

October 29, 2026

SARS-CoV-2 (COVID-19)

Week ending October 17, 2026

Moderate

WVAL: 5.43

Decreasing

5 NWSS sites · 5 monitoring sites

CDC Wastewater Viral Activity Level

Influenza A

Week ending October 17, 2026

Low

WVAL: 3.36

Decreasing

5 NWSS sites · 5 monitoring sites

CDC Wastewater Viral Activity Level

RSV

Week ending October 17, 2026

Very Low

WVAL: 1

Stable

5 NWSS sites · 5 monitoring sites

CDC Wastewater Viral Activity Level

Signal levels use the CDC Wastewater Viral Activity Level (WVAL) methodology. Trend reflects two-week change in Massachusetts median WVAL. Learn more about WVAL methodology.

Current Situation Summary

As of October 17, 2026, the CDC Wastewater Viral Activity Level (WVAL) for SARS-CoV-2 (COVID-19) in Massachusetts wastewater is moderate (decreasing). Moderate and decreasing virus in wastewater suggests that community spread is present but may be decreasing in the wastewater collection area.

As of October 17, 2026, the CDC Wastewater Viral Activity Level (WVAL) for Influenza A & B in Massachusetts wastewater is low (decreasing). Low and decreasing virus in wastewater suggests minimal community spread in the wastewater collection area.

As of October 17, 2026, the CDC Wastewater Viral Activity Level (WVAL) for RSV in Massachusetts wastewater is very low (stable). Low but stable virus in wastewater suggests limited community spread in the wastewater collection area.

Interpreted automatically from CDC NWSS Wastewater Viral Activity Level data. Learn more.

Download SARS-CoV-2 weekly trend data (CSV)

Source: Massachusetts State Public Health Lab and Biobot Analytics. Charts show two respiratory seasons (July 1 – June 30). Dotted line marks the start of the current season. Background shading reflects the CDC Wastewater Viral Activity Level (WVAL) — green: Low/Very Low, yellow: Moderate, red: High/Very High. Learn more about WVAL methodology.

SARS-CoV-2 (Covid-19) – Site Detail

Site-level data from the Massachusetts State Public Health lab. Two-week trends reflect changes in raw wastewater concentration at each site and are independent of the CDC WVAL signal levels shown in the summary above.

The map below shows this same site-level two-week trend geographically, by sewershed (wastewater collection area). The table above presents the identical data in text form and is the recommended way to access this information using a keyboard or screen reader.

Download SARS-CoV-2 site-level data (CSV)

Download Influenza weekly trend data (CSV)

H5N1 (Avian Influenza A)
H5N1 has not been detected at Massachusetts wastewater monitoring sites that contribute to this report. Learn more about H5N1 surveillance.

Flu – Site Detail

Site-level data from the Massachusetts State Public Health Laboratory. Two-week trends reflect changes in raw wastewater concentration at each site and are independent of the CDC WVAL signal levels shown in the summary above.

Download Influenza site-level data (CSV)

Download RSV weekly trend data (CSV)

RSV monitoring in Massachusetts covers 5 sites: MWRA North, MWRA South, South Essex, Upper Blackstone (Worcester), Uxbridge. Coverage may not represent all regions of the state.

RSV – Site Detail

Site-level data from the Massachusetts State Public Health Lab monitoring network. Two-week trends reflect changes in raw wastewater concentration at each site and are independent of the CDC WVAL signal levels shown in the summary above.

Download RSV site-level data (CSV)

Methods and Data Sources

Data Sources

Wastewater concentration data are provided by two laboratories: Biobot Analytics, a wastewater epidemiology company that has collected and analyzed samples from treatment plants across Massachusetts under a Massachusetts Department of Public Health (DPH) contract, and, as of July 2026, the Massachusetts State Public Health Laboratory (DPH), which is progressively taking over in-house testing for a growing set of monitoring sites as the Biobot contract winds down. Each site’s Source is shown in the site detail tables below. Massachusetts reports SARS-CoV-2 wastewater data from a subset of sampled sites to the CDC National Wastewater Surveillance System (NWSS); other Massachusetts sites report data for other pathogens to NWSS independently, but which are monitored by DPH. There are also independent researchers, academic collaborations, and others who do various projects to look at infectious diseases in wastewater which are not represented in this report.

Signal level classifications (Very Low through Very High) are based on the CDC Wastewater Viral Activity Level (WVAL), a standardized metric calculated from NWSS site-level data. WVAL compares current wastewater concentrations to historical baselines at each monitoring site, allowing meaningful comparison across sites and over time regardless of differences in local wastewater characteristics. Learn more about WVAL methodology.

Sewershed (wastewater collection area) boundary polygons are from the MassDEP Estimated Sewer System Service Area Boundaries dataset, maintained by MassGIS and updated October 2025. Boundaries represent approximate service areas for publicly owned treatment works (POTWs) across Massachusetts. The boundaries used in this report are a stored copy of that dataset and are not refreshed automatically; they will not reflect later MassDEP revisions until the copy is manually updated.

Concentration Metric

Charts, site detail tables, and the sewershed map in this report are based on raw (unnormalized) concentration — the number of viral gene copies detected per liter of wastewater, as reported directly by the testing laboratory. Prior versions of this report used Biobot Analytics’ proprietary “effective concentration,” a value normalized for factors such as laboratory detection sensitivity and population served. As of July 2026, this report uses raw concentration instead, for all sites and both laboratories. The Massachusetts State Public Health Laboratory does report a normalized concentration value, but its normalization methodology differs from Biobot’s proprietary effective concentration; raw concentration remains the metric most directly comparable across both laboratories on consistent terms. This choice is also consistent with CDC’s August 2025 update to its own Wastewater Viral Activity Level (WVAL) methodology, which moved to non-normalized inputs so that changes reflect actual changes in wastewater viral levels rather than artifacts of the normalization process.

Raw concentration values reported below a sample’s laboratory-specific limit of detection are set to zero rather than left at whatever small positive value the assay instrument may have reported, so that a formally non-detected result is never counted as if it were a real, low-level signal in trend calculations. This does not affect a sample’s Detected / Not Detected / Quantifiable classification, which is determined independently by comparing the originally reported value to the limit of detection.

Samples from the same site, target, and MMWR week are compared before they are averaged. A non-detect is never treated as disagreeing with a detection. When two detections in a week differ sharply and one departs strongly from the site’s own recent history, that sample is excluded from the week’s average. Excluded samples are removed from the average but remain in the Wastewater Data sheet with their raw values.

Site-level Wastewater Viral Activity Level (WVAL) signal tiles and statewide WVAL trend (see Signal Level Classification and Trend Calculation, below) are unaffected by this metric — WVAL is calculated by CDC directly from the NWSS dataset and does not depend on the concentration values reported in this file.

Wastewater Viral Activity Level (WVAL) Classification

Signal levels are classified into five categories based on CDC WVAL thresholds:

Category	Description
Very Low	Current levels are near or below the historical baseline for this site
Low	Some activity above baseline
Moderate	Meaningful community spread
High	Elevated community spread
Very High	Very high community spread

Thresholds differ by disease and are published by CDC. As of CDC’s August 2026 WVAL methodology update, thresholds are:

	Very Low	Low	Moderate	High	Very High
Influenza A	Up to 2.4	2.4–5.5	5.5–10.2	10.2–15.6	Above 15.6
SARS-CoV-2 (COVID-19)	Up to 2.6	2.6–4.9	4.9–7.9	7.9–11.6	Above 11.6
RSV	Up to 1.7	1.7–3.4	3.4–5.4	5.4–8.1	Above 8.1

CDC recalculates WVAL thresholds periodically using Jenks Natural Breaks applied to the most recent 24 months of wastewater data, so that categories continue to reflect current national wastewater activity rather than a fixed historical benchmark. As of August 2026, CDC also revised several related aspects of the underlying WVAL calculation: extreme values are now Winsorized at the 99th percentile rather than removed outright, new monitoring sites use a laboratory-level baseline and standard deviation for an initial period (182 days for SARS-CoV-2, 365 days for influenza A and RSV) before switching to their own site-level baseline, and CDC’s own national aggregate is now calculated as the median of jurisdictional (state/territory) WVALs rather than the median of regional WVALs. This last change affects only CDC’s national figure; the Massachusetts statewide WVAL shown in this report is calculated independently by DPH as the median of Massachusetts site-level WVALs and is unaffected. Learn more about WVAL methodology.

Influenza B. CDC calculates a Wastewater Viral Activity Level for Influenza A but not for Influenza B, so the Influenza signal tile at the top of this report, its trend arrow, the background shading on the Influenza time series chart, and the Influenza sewershed map all reflect Influenza A only. The chart shading appears behind both lines, but it describes the Influenza A signal level, not a combined or Influenza B level. Influenza B is still tracked in this report: its statewide weekly average concentration is plotted as its own line on the Influenza chart, and each site’s Influenza B two-week trend and Local Signal status are shown as separate rows in the Influenza site detail table.

Chart Time Window

Time series charts display two respiratory seasons of data. Respiratory seasons run from July 1 through June 30. A dotted vertical line marks the boundary between the prior season and the current season. For pathogens where surveillance began after the start of the prior season, charts begin from the first available data point rather than July 1 of the prior year. Chart windows update automatically each July 1 as a new season begins. The line on each time series chart is the unweighted mean of raw concentration across all public monitoring sites reporting that week. It is not weighted by population served, and week-to-week changes can partly reflect which sites reported in a given week.

Trend Calculation

Two distinct trend calculations appear in this report, both using the same two-week-vs-two-week comparison method but different underlying values.

The statewide summary tiles (at the top of this report) show trend based on the CDC Wastewater Viral Activity Level (WVAL), not raw concentration. Trend direction (Increasing, Stable, Decreasing) is calculated by comparing the average statewide WVAL over the two most recent reporting weeks to the average over the two preceding weeks. If the more recent two-week average is more than 20% higher than the prior two-week average, the trend is classified as Increasing; more than 20% lower is Decreasing; within 20% in either direction is Stable. When current WVAL values are very low for both periods (below 1.5), the trend is reported as Stable regardless of percent change, since small fluctuations near the detection floor are not epidemiologically meaningful.

The site detail tables’ 2-Week Trend column and the sewershed map instead use each site’s own raw concentration (see Concentration Metric, above), with outlier-flagged weeks excluded (see Outlier Detection, below). The same 20%-threshold comparison method applies, but computed per site rather than statewide, and on concentration rather than WVAL. These two trend calculations can legitimately disagree — a site’s own two-week concentration trend and the statewide WVAL trend are answering related but different questions, and Massachusetts’s NWSS-reporting sites do not fully overlap with this report’s own monitoring network.

A site is marked “New detection” when its prior two-week window contains no detected sample and its latest window does. No percent change is reported in this case, because a change from zero is undefined. The flag indicates that a detection has appeared after a period of non-detection. It does not confirm a sustained increase, and it stays in the table until a following week of data either supports or contradicts it.

When one week in a site’s two-week window is excluded, the average and trend use the remaining valid week. The row is labeled Recent week under review, and the average may then reflect a single week.

Trend is not reported when both the latest and prior periods are zero. When the prior period is zero and the latest period is above zero, the New detection label applies rather than a percent change.

Site-Level Signal Detection (Covid and Flu)

The SARS-CoV-2 and Influenza site detail table include a Local Signal column that flags individual monitoring sites showing signs of a localized surge, independent of the statewide WVAL signal level. A site is flagged as Elevated when at least two of the following three criteria are met over a six-week lookback window:

C1: The current two-week average concentration exceeds the maximum concentration recorded at that site over the prior six weeks
C2: The current two-week average is at least 50% higher than the two-week average immediately preceding it
C3: The site is currently detecting virus after six or more consecutive weeks of non-detection (re-emergence)

This approach is adapted from the Covid-SURGE algorithm described in Keshaviah et al. (2023), Separating signal from noise in wastewater data: An algorithm to identify community-level COVID-19 surges in real time (PNAS). Sites meeting the Elevated threshold are sorted to the top of the table. The Local Signal flag reflects facility-level concentration dynamics only and should be interpreted alongside — not instead of — the statewide WVAL signal level. As of July 2026, this calculation uses concentration with outlier-flagged weeks excluded (see Outlier Detection, below), so a single anomalous lab or reporting artifact cannot trigger a false Elevated flag; the detect/non-detect determination behind criterion C3 is unaffected by outlier flagging.

Outlier Detection

Independent of the Local Signal / SURGE algorithm above, each site’s raw concentration history for SARS-CoV-2, Influenza, and RSV is screened for statistical outliers — values that look like a lab or reporting artifact rather than a genuine result. This is a data-quality check, not a signal-detection check: SURGE (above) asks “is this a real rise worth highlighting?”; outlier detection asks “is this value trustworthy enough to feed into the trend calculations at all?” RSV is included in outlier detection even though it is excluded from SURGE — RSV’s small number of monitoring sites is a reason to exclude it from signal detection, but not from a data-quality check.

A site-week’s average concentration is flagged as a candidate outlier when it falls more than 3.5 median absolute deviations (MAD) from that same site’s own trailing six-week median, computed on a log scale to account for the right-skewed nature of concentration data. Each site is compared only against its own history, never against other sites, since absolute concentration varies enormously with sewershed population and dilution — the same reason WVAL is baseline-relative rather than absolute. A site needs at least six weeks of trailing history before it is eligible to be flagged, so a site’s first few real samples are never flagged simply for lack of a baseline.

A candidate alone is not treated as a confirmed artifact, because a real, sustained rise or fall can look identical to a one-off lab error for several weeks — a six-week median doesn’t fully “catch up” to a genuine trend until most of that window has turned over, so the early weeks of a real wave can otherwise be mistaken for repeated artifacts. To avoid this, each candidate is checked against the following week’s data before being finalized: if the next sample still deviates from the same pre-candidate baseline in the same direction, the shift is treated as real and the candidate week is folded back into the trend calculations. If the next sample instead reverts back toward the prior baseline, that confirms the candidate really was a one-off, and it is excluded as a confirmed Outlier. A candidate week with no next-week sample yet to check against — most often the most recent week in the dataset — is shown as a Possible outlier: excluded from trend calculations in the meantime, but not yet a settled determination, and will either clear or become a confirmed Outlier once the following week’s sample arrives.

Both Possible outlier and confirmed Outlier weeks are excluded from the weekly trend charts, the SURGE calculations above, and the sewershed map — but a Possible outlier’s exclusion does not retroactively alter the trailing baseline used to assess weeks after it, so a confirmed, sustained rise correctly stops being excluded once the following week’s sample confirms it. In the site tables, a site’s average and trend use its remaining valid weeks. A Possible outlier label replaces the trend only when no valid week remains in the window.

Outlier flagging affects concentration values only. It never affects a sample’s Detected / Not Detected / Quantifiable status, which is determined independently (see Concentration Metric, above). A flagged sample continues to display its actual detection status.

A candidate is not evaluated when its trailing six-week baseline is entirely non-detect. A detection following a run of non-detects is treated as a real signal, and it remains in the trend until a following week of data supports or contradicts it.

Data Completeness in Site Detail Tables

Site-level detail tables rely on a consistent reporting cadence to calculate two-week trends and facility-level signal flags. The tables use the labels below when a site’s data is incomplete, excluded, or otherwise needs context.

“No recent data” appears when a site has not reported a sample within the most recent two-week window, but has an active sampling history within the past 90 days. The site remains listed with its most recent available result and sample date. Trend and, for SARS-CoV-2 and Influenza, Local Signal status are not calculated for that period. Sites that have not reported in more than 90 days are removed from the table, because they are no longer considered active in the surveillance network.

“Possible outlier” appears when a site reported a sample within the most recent two-week window, but that sample’s concentration was flagged as a statistical outlier and is awaiting confirmation from the following week’s sample (see Outlier Detection, above). No valid week remains in the window, so no average or trend is shown. The site still shows its detection status. The flag may clear once the following week’s sample arrives, in which case the site returns to its normal trend.

“Recent week under review” appears when one week in a site’s two-week window has been flagged as an outlier and excluded, and the remaining week is valid. The average and trend are calculated from the valid week. Because the average may then reflect a single week, read the trend with that in mind. The label is a caution, not a judgment that the valid week is wrong.

“Outlier excluded” appears when a site reported a sample within the most recent two-week window, the flagged value was confirmed as a data-quality artifact by the following week’s sample, and no valid week remains in the window. Unlike “Possible outlier,” this is a settled determination.

“Not Detected” appears when every usable sample in the two-week window was below the limit of detection. The average is shown as zero, which is a placeholder for a non-detect result rather than a measured concentration. The trend is not reported.

“Insufficient data” applies specifically to the Local Signal column for SARS-CoV-2 and Influenza. It indicates that a site’s sampling history has too many gaps over the relevant lookback window to reliably evaluate the surge criteria described above. This can happen because the current two-week window is incomplete, or because too many weeks are missing from the six-week lookback used for criteria C1 and C3. It is distinguished from “Elevated” and from “—,” both of which require a sufficiently complete reporting history to calculate.

Influenza wastewater monitoring at most Massachusetts sites currently follows a less frequent sampling cadence than SARS-CoV-2, so more missing lookback weeks are tolerated before a site is marked “Insufficient data” for Influenza. This threshold will be tightened as Influenza surveillance matures and sampling frequency increases across the network.

Notes on the trend and average display. In the concentration column, “<0.1” means a detection that rounds to zero at the displayed precision (about 50 copies/L or less). A dash (“—”) means no usable value. “New detection” in the trend column means the most recent two weeks contain a detection after a period with none, and no percent change is reported because a change from zero is undefined.

Sewershed (wastewater collection area) Map

The sewershed map displays the two-week wastewater trend for each monitored treatment plant’s service area. Sewersheds are colored by whether concentration is increasing, stable, or decreasing relative to the prior two weeks. The map uses the same site-level trend calculation as the site detail tables (see Trend Calculation, above), including the same handling of missing data and outlier-flagged samples, so a sewershed’s color on the map matches the 2-Week Trend shown for that site in the table. Sewersheds where a monitored site has a New detection are shown in blue; this flag indicates a detection after a period of non-detection and is not yet confirmed by a following week. The Influenza map shows Influenza A only, consistent with the Influenza signal tile and chart shading; Influenza B site-level trends are available in the Influenza site detail table.

Each shaded area represents the estimated sewered portion of a single town served by that treatment plant. Parts of a town on septic systems, or served by a different treatment plant, are not included. Selecting an area shows the town, the sewershed (treatment plant) serving it, and that sewershed’s current trend and two-week average concentration. Where a treatment plant has more than one sampling location, the sewershed is shaded by the most concerning trend among them (Increasing, then Stable, then Decreasing), so that a rise at one sampling point is not masked by the others, and the concentration shown is the average across those sampling locations.

Coverage is not uniform. Areas shown in light grey are not served by a currently monitored treatment plant, including plants that have not reported in more than 90 days. Areas shown in medium grey are served by a monitored treatment plant whose trend could not be assessed for the current period, for example because no sample was reported in the most recent two weeks or the most recent sample was excluded as an outlier (see Data Completeness in Site Detail Tables, above). The Massachusetts Water Resources Authority (MWRA) Deer Island system is split into its North and South service areas, each monitored independently.

Site Coverage

This report presents data from community wastewater treatment plants across Massachusetts. The number of sites varies by pathogen, reflecting the current capacity of the surveillance program. Not all regions of the state are represented equally — results should be interpreted as indicators of statewide trends rather than precise local estimates. Site coverage will continue to vary over time.

Limitations

Wastewater data reflect community-level trends and cannot be used to estimate the number of individual infections.
Site coverage is not uniform across the state; some regions may be over- or under-represented.
WVAL requires a minimum period of historical data to establish a reliable baseline. Signal levels for newer pathogens may be less stable as baseline data accumulate.
Wastewater signal can be influenced by factors unrelated to infection, including rainfall, population changes, treatment plant operations, and the size of the sewershed.
Sewersheds often cover parts of multiple communities and do not always respect existing geographical boundaries.
Sewershed boundaries are approximate and represent estimated service areas; precise boundaries may differ from those shown.

About This Surveillance Program

This report is produced by the Massachusetts Department of Public Health (DPH) Bureau of Infectious Disease and Laboratory Sciences (BIDLS). For more information about DPH infectious disease surveillance, visit mass.gov/DPH.