How to Read CDC and Local Outbreak Alerts Alongside AQI

Last updated May 20, 2026 · 8 min read

AirNow tells you what the air is doing. CDC tells you what respiratory viruses are doing. Most days these are independent decisions. But during a smoke event or an outbreak wave — and especially when both happen at once — the two feeds belong on the same dashboard. This guide breaks down what each data source actually measures, the lag and resolution each has, and how to combine them for one coherent household decision.

The AQI feed in 60 seconds

AirNow is operated by the U.S. EPA, NOAA, and partner agencies. It ingests measurements from roughly 2,000 regulatory air-quality monitors, computes the Air Quality Index for the six criteria pollutants, and publishes both real-time values and 24-hour forecasts. For deeper background, see our How AirNow Data Works guide. Two things to remember:

• The AQI value you see is for the dominant pollutant. If PM2.5 is at AQI 110 and ozone is at AQI 70, the displayed AQI is 110 (PM2.5).
• The number has built-in smoothing. The NowCast algorithm gives more weight to recent hours during stable conditions and less during rapidly-changing conditions. The headline number can lag a sudden smoke arrival by 1–3 hours.

The CDC respiratory-illness feeds in 60 seconds

The CDC publishes multiple streams about respiratory virus activity. They measure different things and update on different schedules:

ILI / Outpatient surveillance (FluView, ILINet)

Sentinel outpatient providers report the proportion of patient visits for influenza-like illness. National rollup updates weekly (Fridays for the week ending the previous Saturday). It's a leading indicator of respiratory-virus circulation overall, not just influenza — a high ILI signal often precedes hospitalization signals by 1–2 weeks.

Hospitalization surveillance (RESP-NET, COVID-NET)

Lab-confirmed hospitalizations for influenza, RSV, and COVID-19 in defined catchment populations. Used to estimate true population incidence. Updates weekly with a 1–2 week lag — the most reliable severity signal but the slowest.

Wastewater surveillance (NWSS)

SARS-CoV-2 and (more recently) influenza and RSV RNA levels in municipal wastewater at participating treatment plants. Updates every few days. Wastewater is the earliest signal — it leads case counts and hospitalizations by 4–10 days because it captures all infected people, not just those who tested.

Emergency-department visits (NSSP)

National Syndromic Surveillance Program data on ED visits for respiratory complaints. Updates daily for participating jurisdictions. Faster than hospitalization data, noisier than wastewater.

You don't need to track all of these directly. CDC's combined Respiratory Virus Dashboard rolls the streams into a single regional readout, and Pandemic Watch publishes the same picture in a more readable format with state-level breakdowns.

State and county feeds

State and county health departments publish their own outbreak data, sometimes with finer geographic resolution and faster cadence than CDC. The variation across jurisdictions is large — California's CalREDIE and Massachusetts's MAVEN are mature; many states publish only weekly PDFs. If you live in a metro with significant air-quality and outbreak dual-risk (Los Angeles, Sacramento, Phoenix, Denver, Salt Lake City, Portland, Seattle), check whether your county dashboard publishes daily wastewater or ED-visit data — those are the fastest local signals.

A simple combined readout

For household decisions, you usually don't need fine-grained pollutant breakouts or virus-by-virus splits. A two-axis mental model works well:

"Active wave" here roughly means: regional ED visits or wastewater above the seasonal baseline trendline. "Severe outbreak" means above the 90th percentile for that geography. The thresholds your jurisdiction publishes will be more precise than this rough cut.

Setting up alerts

Both feeds will let you push alerts to your phone, with some setup:

• AirNow / Smog Report — Smog Report's Live Activities show current AQI from your nearest EPA monitor; widget and notification options trigger on color changes. The EPA AirNow app also offers basic alerts for free.
• CDC — does not push to consumers directly. State health departments often have email or SMS alerts for serious advisories.
• Pandemic Watch — pandemicwatch.org publishes the combined picture with weekly updates.

Caveats and what this doesn't replace

Public-health surveillance data describes population-level trends, not individual exposure or individual risk. The above table is a rough mental model, not a medical recommendation. People with significant respiratory or cardiovascular conditions should set personal thresholds in conversation with their physician — and recognize that during stacked events the threshold should usually be lower than for either input alone. See AQI and Outbreaks for the biology underlying that interaction.

Primary sources: EPA AirNow · CDC Respiratory Virus Data Dashboard · CDC National Wastewater Surveillance System · Pandemic Watch