Disease Surveillance

Your wastewater is an early warning system for outbreaks — before most people know they're sick.

Every day, viruses shed by infected people flow into the sewer system. Scientists can detect them in water samples days before cases show up in clinics or hospitals — giving communities a head start on what's coming.

National · COVID-19 · 2021–2025

Five years of COVID-19 in US wastewater

Monthly median virus concentration across CDC-monitored treatment plants. Each spike marks a variant wave — often detectable in sewers weeks before hospitals felt the surge.

California · Five diseases · 2023–2026

What's circulating in California's wastewater right now

Each disease is shown as a percentage of its own highest recorded level, so all five are directly comparable. 100% means the worst week on record for that pathogen; 0% means none detected.