"Facebook has been showing a survey to users within the social network. Users can take this survey if they want to - it's entirely voluntary. They'll answer questions about whether they're experiencing symptoms associated with COVID-19, such as cough or fever.
That data then gets sent to the research team at Carnegie Mellon (not Facebook), which uses it to create population models of people experiencing symptoms. The idea is that symptoms are the "precursor" to hospital visits, so an uptick in symptoms in a particular area could help officials decide where to send health resources.
"The survey responses combined with other data such"