COUNTY SURVEILLANCE

Cook County

Name: COVID Flow Illinois wastewater activity indices
Creator: COVID Flow
License: https://www.usa.gov/government-works

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

Activity index

-2.22

Week over week +1.5%

Stable

Updated Jun 15, 2026

Activity index

-2.22

Week-over-week +1.5%

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

Sites reporting

15 of 19 registered sewersheds · 6.8M population represented

Data quality

78%

Latest week composite score. See quality panel for flags.

How to read the activity index

Near zero

Typical shedding for that sewershed compared with its own history.

Below zero

Less viral RNA than the historical baseline for that location.

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 Jun 15. Sorted by activity index (highest first).

Site ID	Counties served	Activity	WoW	Trend	Quality	Last sample
414	Cook	-1.07	+53.9%	Rising	85%	Jun 17
423	Cook	-1.67	+83.9%	Rising	85%	Jun 17
421	Cook	-2.04	-5.9%	Stable	85%	Jun 18
416	Cook	-2.08	-66.6%	Falling	80%	Jun 17
419	Cook	-2.14	-4.1%	Stable	85%	Jun 17
431	Cook	-2.15	+110.3%	Rising	85%	Jun 17
427	Cook	-2.16	-86.6%	Falling	85%	Jun 18
428	Cook	-2.26	-133.4%	Falling	85%	Jun 17
413	Cook	-2.28	0.0%	Stable	65%	Jun 17
424	Cook	-2.34	0.0%	Stable	80%	Jun 18
425	Cook	-2.39	0.0%	Stable	80%	Jun 17
429	Cook	-2.63	0.0%	Stable	65%	Jun 17
418	Cook	-2.65	0.0%	Stable	80%	Jun 18
430	Cook	-3.18	-133.1%	Falling	65%	Jun 17
417	Cook	-3.32	-37.5%	Falling	65%	Jun 17

Data quality

How complete and reliable the underlying wastewater samples are for the latest reporting week. Lower scores mean more caution when interpreting trends.

78%quality score

Some samples below limit of detection
Sample location is not a wastewater treatment plant
Missing flow or population normalization
Grab sample rather than composite collection

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 cleaning rules, and roll samples up to site and region level. Cook County views use Illinois-focused cleaning rules before publishing to this dashboard.

Source: CDC NWSS program

Projected trend (next few weeks)

Our best estimate of where the wastewater activity index for Cook County is heading over the next few weeks, shown with an uncertainty band. This tracks wastewater activity, not confirmed case counts.

Short-horizon forecast

Ensemble baseline for Cook County from the week of Jun 15. Shaded band ≈ 80% interval from backtest errors.

Viewing: Ensemble baseline

Rising

ObservedEnsemble~80% interval

1-week outlook (ensemble_v1): Rising · confidence high. Surveillance context only, not for clinical decisions.

Current metrics

Historical trend

Sewershed sites

Quality and provenance

Projected trend (next few weeks)