COVID-19 World Survey Data API

An open API from the University of Maryland

Go to the documentation for the World Survey Data API.


We are currently working to fine-tune our data weighting, aggregation and smoothing methods. As a result, the query responses returned by the API could be subject to change.

About Our Data

This COVID-19 indicators are derived from the world symptoms surveys that are placed by Facebook on its platform. The surveys ask respondents how many people in their household are experiencing COVID-like symptoms, among other questions. These surveys are voluntary, and individual survey responses are held by University of Maryland and are shareable with other health researchers under a data use agreement. No individual survey responses are shared back to Facebook. Using this survey response data, we estimate the percentage of people in a given geographic region on a given day who have CLI (COVID-like illness = fever, along with cough, shortness of breath, or difficulty breathing) or ILI (Influenza-like illness = fever, along with cough or sore throat).

About Our Methodology

The detailed method description is listed in this document and this document. Our API design is inspired by Delphi’s COVIDcast API from Carnegie Mellon University. If you are interested in other open Epidemiological Data API, please go check out delphi-epidata.

Live Estimates

The daily COVID-19 indicators returned by our data API represent are our best estimates given all data that we have available up until now. The estimates for the indicator values for current day would typically be available two days later due to the data weighting and aggregation process.

Smoothed Estimates

For each smoothed indicator, our estimates are derived using data smoothing techniques (akin to averaging, or weighted averaging) across an one week window. Smoothed estimates aggregate survey responses from multiple days for a geographic region. As a result, more geographic regions will have smoothed estimation results in comparison with daily live estimates.

Missing Estimates

Generally, we do not report estimates at locations with insufficient survey responses (or insufficiently recent data).

Release Log