When an infectious disease starts spreading, it seldom takes its time. And when that infection is called Ebola, any delay in halting its spread can take a very real toll in human lives. The trouble, of course, is that it takes time for people to even figure out that an outbreak has occurred. Thankfully, machines are getting smarter.

Nine days before the World Health Organization announced the African Ebola outbreak now making headlines, an algorithm had already spotted it. HealthMap, a data-driven mapping tool developed out of Boston Children’s Hospital, detected a “mystery hemorrhagic fever” after mining thousands of web-based data sources for clues.

“We’ve been operating HealthMap for over eight years now,” says cofounder Clark Freifeld. “One of the main things that has allowed it to flourish is the availability of large amounts of public event data being accessible on the Internet.”

Those data sources include news reports, social media, international health organizations, government websites, and even the personal blogs of health care workers operating in affected areas. The team’s custom-built web crawler traverses RSS feeds and APIs, analyzing the text from these content sources for disease-related terminology and clues about geography.

As anyone who’s ever looked at the Internet knows, any bulk consumption of web content is bound to scoop up tons of noise, especially when sources like Twitter and blogs are involved. To cope with this, HealthMap applies a machine learning algorithm to filter out irrelevant information like posts about “Bieber fever” or uses of terms like “infection” and “outbreak” that don’t pertain to actual public health events.

“The algorithm actually looks at hundreds of thousands of example articles that have been labeled by our analysts and uses the examples to pick up on key words and phrases that tend to be associated with actual outbreak reports,” explains Freifeld. “The algorithm is continually improving, learning from our analysts through a feedback loop.”

The latest string of Ebola infections became public knowledge on March 23 when the World Health Organization issued its first report on it. Since then, the outbreak–which appears to have started with a 2-year-old boy in Guinea–has spread to other countries in Africa and killed over 1,000 people.