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

-2.15

Week over week -6.6%

Stable

Updated Jul 13, 2026

Activity index

-2.15

Week-over-week -6.6%

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

Sites reporting

16 of 19 registered sewersheds · 6.8M population represented

Data quality

81%

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.

16 of 19 sewersheds reported for the week of Jul 13. Sorted by activity index (highest first).

Site ID	Counties served	Activity	WoW	Trend	Quality	Last sample
419	Cook	-1.48	+88.0%	Rising	85%	Jul 15
417	Cook	-1.62	+54.3%	Rising	85%	Jul 15
425	Cook	-1.68	+61.2%	Rising	100%	Jul 15
431	Cook	-1.72	+23.1%	Stable	85%	Jul 15
414	Cook	-1.78	-47.6%	Falling	80%	Jul 15
422	Cook	-1.82	+86.6%	Rising	100%	Jul 17
427	Cook	-1.85	+67.1%	Rising	100%	Jul 17
416	Cook	-1.97	0.0%	Stable	80%	Jul 15
428	Cook	-2.11	-22.4%	Stable	85%	Jul 15
418	Cook	-2.15	+40.9%	Rising	85%	Jul 16
413	Cook	-2.19	0.0%	Stable	65%	Jul 15
424	Cook	-2.22	0.0%	Stable	65%	Jul 14
421	Cook	-2.35	-4.3%	Stable	85%	Jul 17
423	Cook	-2.41	-43.2%	Falling	65%	Jul 15
429	Cook	-2.54	-78.6%	Falling	65%	Jul 15
430	Cook	-3.05	-130.2%	Falling	65%	Jul 15

Data quality

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

81%quality score

Some samples below limit of detection
Sample location is not a wastewater treatment plant
Missing flow or population normalization

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 Jul 13. 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)