Data & Methodology

Contagions.us turns official surveillance into a readable state snapshot without turning signals into diagnoses.

Overall acute respiratory illness (ARI)

CDC ARI activity reflects the percentage of emergency-department visits involving acute respiratory illness. CDC supplies the state classification: Very Low, Low, Moderate, High or Very High.

Source: CDC dataset f3zz-zga5.

Wastewater viral activity

CDC wastewater levels describe SARS-CoV-2, Influenza A or RSV signal relative to historical measurements. They do not equal the percentage of people infected and are not the same metric as clinical illness.

State classifications come from the machine-readable feed used by the CDC state page. The official sampling-site dataset is CDC dataset atcp-73re.

Trends, lag and coverage

A change appears only when comparable current and previous categories exist. Data can lag and be revised. Insufficient coverage remains Limited / No Data rather than being estimated.

Refresh safeguards

Weekly tooling validates sources and coverage, checks a temporary file, and atomically replaces the last-known-good snapshot.