What does the wastewater percentile mean?

Each site's latest sample is scored 0–100 against that same site's history — 80+ means near that site's historical highs. People shed virus before they feel sick, so rising wastewater levels are an early-warning signal that can lead reported cases by days.

Is this real CDC data?

Yes — the CDC's public NWSS SARS-CoV-2 dataset on data.cdc.gov, queried directly and aggregated in your browser. Values are shown as published.

Do I need an API key?

No. The Socrata endpoint is public, key-less and CORS-enabled.

Does it work offline?

No — it needs an internet connection to query data.cdc.gov; offline it shows a short notice.

Yes — free, no download, in your browser.

Does a high wastewater level mean I will get sick?

It means more virus is showing up in that sewershed than is usual for it. It is a community-level indicator and says nothing about any individual's risk.

Why can't different states be compared directly?

Each site is measured against its own past levels, and sites differ in size and sampling schedule. A state at the same percentile as another is similarly elevated for itself, not necessarily similar in absolute virus.

Wastewater Virus Levels Screensaver

The Wastewater Virus Levels screensaver ranks US jurisdictions by SARS-CoV-2 levels in wastewater, from the CDC's National Wastewater Surveillance System dataset on data.cdc.gov. Each state's number is the average of its treatment plants' latest site percentiles. It's free, needs an internet connection, and ESC exits.

How the Wastewater Virus Levels screensaver works

Your browser queries the CDC's NWSS dataset on data.cdc.gov (key-less, CORS-enabled Socrata API) hourly.

It first asks the dataset for its newest sample date, then pulls the last two weeks of reports relative to that — so the board shows whatever CDC has most recently published, even if reporting lags.

Each treatment plant reports a 0–100 percentile of its latest sample against that site's own history; the board averages sites per jurisdiction and ranks them.

Colors band the average: green low, amber elevated, red near historical highs.

How wastewater surveillance works

Public-health labs take regular samples of the wastewater arriving at treatment plants, measure the concentration of viral genetic material and track how it changes. The CDC’s National Wastewater Surveillance System draws on data from state, territorial and local health departments, CDC’s national wastewater testing contract and an academic partner group, WastewaterSCAN, and publishes it in a shared dataset. CDC currently tracks several pathogens, including COVID-19, influenza A, RSV, measles, avian influenza A (H5) and mpox.

Its main value is timing and coverage. CDC notes that wastewater data do not depend on people having symptoms, seeing a doctor or having access to testing, that results can take about 5 to 7 days from flush to result, and that they can give early warning, often before people reach doctors or hospitals. One treatment plant can reflect trends for a large population. But most reporting comes from municipal systems in urban and suburban areas, and estimating how many people are sick is difficult because shedding varies with severity and viral strain.

The percentile used here compares a site’s latest sample with that same site’s own history, so a high figure means high for that place, not high compared with other places. Averaging plants into a state number blends sites that differ in size and reporting frequency. CDC describes the data as preliminary, so interpret the board as a rough trend signal.

A worked example

If Utah's plants average a percentile of 84 while another state's sit at 12, Utah tops the board in red — a hint that infections may be rising there before case counts show it. The site count next to each name tells you how much signal is behind the average. In Multi-view it pairs well with the other health boards.

Settings & tips

Jurisdictions shown sets how many rows the ranking keeps (10–20).
The header shows the newest sample date in the dataset — NWSS reporting can lag or pause, and the board shows that date honestly.
States with only a site or two swing harder; check the per-row site count before reading too much into a rank.

Frequently asked questions

What does the wastewater percentile mean?: Each site's latest sample is scored 0–100 against that same site's history — 80+ means near that site's historical highs. People shed virus before they feel sick, so rising wastewater levels are an early-warning signal that can lead reported cases by days.
Is this real CDC data?: Yes — the CDC's public NWSS SARS-CoV-2 dataset on data.cdc.gov, queried directly and aggregated in your browser. Values are shown as published.
Do I need an API key?: No. The Socrata endpoint is public, key-less and CORS-enabled.
Does it work offline?: No — it needs an internet connection to query data.cdc.gov; offline it shows a short notice.
Is it free?: Yes — free, no download, in your browser.
Does a high wastewater level mean I will get sick?: It means more virus is showing up in that sewershed than is usual for it. It is a community-level indicator and says nothing about any individual's risk.
Why can't different states be compared directly?: Each site is measured against its own past levels, and sites differ in size and sampling schedule. A state at the same percentile as another is similarly elevated for itself, not necessarily similar in absolute virus.
Which viruses can wastewater testing track?: CDC's program tracks several pathogens, including COVID-19, influenza A, RSV, measles, avian influenza A (H5) and mpox. This board shows only the SARS-CoV-2 measure.

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