CDC Epidemic Trends and Rt: Weekly COVID-19 and Flu Estimates by State

CDC Epidemic Trends and Rt is an archive of estimated trend categories, probabilities of epidemic growth, and effective reproduction numbers (Rt) for COVID-19 and influenza, updated weekly. Estimates are generated by the CDC's Center for Forecasting and Analytics using emergency department visit data from the National Syndromic Surveillance Program (NSSP), with modeling methods updated on June 1, 2026. The dataset was last updated on 2026-06-04.

Use Cases

• Forecast epidemic trends for a specific disease and state using date, median, lower, and upper columns.
• Classify the probability of epidemic growth (p_growing) and trend category (category) based on Rt estimates.
• Analyze the uncertainty of Rt estimates by calculating confidence intervals from lower, upper, and interval_width columns.
• Track the evolution of modeling methods by comparing estimates before and after the 2026-06-01 change using the as_of column.

Strengths

• Data is updated weekly, with the last update recorded as 2026-06-04 21:17:47.
• Estimates include uncertainty metrics (lower, upper, interval_width) and a probability of growth (p_growing).
• Covers two major respiratory diseases (COVID-19 and flu) across U.S. states, as indicated by the disease and state columns.
• Modeling methodology is documented and publicly available, with a noted change in methods on June 1, 2026.

Limitations

• Row count and total dataset size are unknown, which may limit suitability assessment.
• License and author information are not provided in the input metadata.

Provenance

Source

data.cdc.gov, based on emergency department visits reported to the National Syndromic Surveillance Program (NSSP).

Collection Method

Estimates generated using nowcasting models; methods changed from a semi-mechanistic Bayesian model (EpiNow2) to a hierarchical generalized additive model (HGAM) on 2026-06-01.

Time Range

Temporal coverage is implied by weekly updates and the date column; specific range is not stated.

Freshness

Updated weekly; last updated 2026-06-04.

Geography

Spatial coverage includes U.S. states, as indicated by the state column.