The Ebola outbreak in West Africa is focusing a spotlight on an online tool run by experts in Boston that flagged a "mystery hemorrhagic fever" in forested areas of southeastern Guinea nine days before the World Health Organization formally announced the epidemic.

HealthMap uses algorithms to scour tens of thousands of social media sites, local news, government websites, infectious-disease physicians' social networks and other sources to detect and track disease outbreaks. Sophisticated software filters irrelevant data, classifies the relevant information, identifies diseases and maps their locations with the help of experts.

"It shows some of these informal sources are helping paint a picture of what's happening that's useful to these public health agencies," HealthMap co-founder John Brownstein said.

HealthMap is operated by a group of 45 researchers, epidemiologists and software developers at Boston Children's Hospital.

The tool was introduced in 2006 with a core audience of public health specialists, but that changed as the system evolved and the public became increasingly hungry for information during the swine flu pandemic.

HealthMap generates information that includes locations of specific outbreaks and tracks new cases and deaths. The system is also capable of logging public sentiment.

The Ebola outbreak, the largest and longest ever recorded for the disease, has so far killed more than 950 people. It emerged in Guinea in March and has since spread to Sierra Leone, Liberia and Nigeria.