Speaking at Fortune‘s Brainstorm Health virtual event, Dr. John Brownstein, who helped create HealthMap in 2006, explained how combining disparate digital clues—such as unusual hospital parking lot activities—is critical to detecting and managing outbreaks of COVID-19 and other diseases.

Brownstein pointed to an uptick in searches related to coughs and diarrhea on Baidu, China’s main search engine, as another early source of evidence of the outbreak.

HealthMap works by pulling in vast amounts of data from publicly available sources, including news reports, government agencies and academic publications. Its software, which scans sources in nine different languages, then compiles the data in public repositories available on the software-development site GitHub for other researchers to parse.

The goal is to “bridge digital sources to detect outbreak,” said Brownstein, who is also chief innovation officer at Boston Children’s Hospital. He added that the process is both more comprehensive and much cheaper than many similar initiatives carried out by government agencies.

In response to the current pandemic, HealthMap has helped launch “Covid Near You,” a sister tool to the long-established “Flu Near You.” Both services, available as websites and apps, rely on members of the public to submit their symptoms so as to help track outbreaks across the country.

Brownstein says the data HealthMap collects can not only help detect outbreaks, but help inform responses too. Health authorities, for instance, can assess how receptive a given population will be to receiving COVID-19 vaccines based on what percentage of that population has historically received flu shots.

All of this points to an increasingly data-driven approach to health policy, and one that relies on contributions from the public as well as from scientists.

“It’s putting the public back in public health,” Brownstein says.