CDC NSSP Emergency Department Surveillance
- Source
- CDC National Syndromic Surveillance Program
- Update Cadence
- Weekly
- Coverage
- Most states (participation varies)
- Official URL
- View source
What It Measures
The National Syndromic Surveillance Program (NSSP) tracks the percentage of emergency department (ED) visits that are related to specific syndromes, including COVID-like illness (CLI) and influenza-like illness.
How It Works
NSSP collects electronic health data from approximately 73% of U.S. emergency departments. Chief complaints and diagnosis codes are used to classify visits into syndrome categories.
What It Tells You
NSSP captures a different population than ILINet — people who go to the emergency room rather than their regular doctor. ED visits tend to represent more severe illness, so NSSP can signal when respiratory illness is causing enough concern for ER visits.
Limitations
- Not all states participate equally, so geographic coverage varies.
- ED visit patterns are affected by non-illness factors (holidays, weather, hospital capacity).
- Classification of visits into syndromes is based on keywords and codes that may not always be accurate.