COVID Flow

COUNTY SURVEILLANCE

Cook County

Cook County and Chicago-area sewersheds. A metro-focused view of community viral shedding in wastewater.

Activity index

-1.66

Week over week +63.4%

Rising

Updated May 4, 2026

Current metrics

Activity index

-1.66

Week-over-week +63.4%

Compared to each sewershed's own history (0 = typical week)

Sites reporting

15

15 of 19 registered sewersheds · 6.8M population represented

Data quality

89%

Latest week composite score. See quality panel for flags.

How to read the activity index

01

Near zero

Typical shedding for that sewershed compared with its own history.

02

Below zero

Less viral RNA than the historical baseline for that location.

03

Above zero

More viral RNA than the historical baseline for that location.

Week-over-week change shows direction only. Trend labels (rising, falling, stable) apply only when enough samples meet our quality thresholds.

Historical trend

Weekly community wastewater signal for Cook County, aggregated from CDC NWSS sewershed samples after cleaning and quality review.

Wastewater activity over time
Weekly weighted activity index for Cook County. Higher values indicate elevated viral RNA relative to the regional baseline.

Source: CDC NWSS via COVID Flow weekly pipeline. Index is relative to historical sewershed baselines, not a case count.

Sewershed sites

Site-level activity for the latest reporting week. Each row is one wastewater monitoring location connected to the public sewer network.

15 of 19 sewersheds reported for the week of May 4. Sorted by activity index (highest first).

Site IDCounties servedActivityWoWTrendQualityLast sample
423Cook-0.92+136.3%Rising85%May 6
416Cook-0.95+40.2%Rising85%May 6
413Cook-1.21+125.0%Rising85%May 6
417Cook-1.26+58.6%Rising85%May 6
418Cook-1.29+125.0%Rising100%May 7
428Cook-1.37+79.7%Rising100%May 6
425Cook-1.42+9.4%Stable100%May 6
419Cook-1.90+136.5%Rising85%May 6
414Cook-1.91-25.8%Falling80%May 6
424Cook-2.01-108.0%Falling100%May 7
421Cook-2.01-33.2%Falling100%May 7
429Cook-2.07-46.3%Falling85%May 6
430Cook-2.68+7.6%Stable85%May 6
431Cook-2.80+3.3%Stable85%May 6
427Cook-2.83-180.2%Falling80%May 7

Quality and provenance

Data quality
How complete and reliable the underlying wastewater samples are for the latest reporting week. Lower scores mean more caution when interpreting trends.
89%quality score
  • Some samples below limit of detection
  • non wwtp location
  • missing flowpop norm
  • grab sample

Wastewater monitoring reflects community shedding, not individual diagnoses. Gaps in sampling, lab methods, or sewershed coverage can shift the index without a true epidemic change.

Data provenance
Metrics are rebuilt each week from CDC NWSS open data. We harmonize sewershed identifiers, apply Illinois-focused cleaning rules, and roll samples up to the site and region level before publishing to this dashboard.

Source: CDC NWSS program

Short-horizon forecast
We are validating Neural ODE based projections with uncertainty bands. Until models pass held-out evaluation, use the historical chart for trend context only.

Forecast module in development · expected in a future release after model review