(Chicago Tribune) -- Dr. Andrea Dugas recalled widespread skepticism at a medical conference a few years ago when a colleague suggested that social media mentions and search volume could one day forecast flu activity.

"They would say, 'How can you use this social media to surveil flu data?' and 'It's crazy' and 'You can't do that,'" said Dugas, a Johns Hopkins University professor who studies flu-tracking. "Now it's widely acceptable."

Chicago is experiencing what health officials have called its earliest and most active flu season in nearly a decade. The federal Centers for Disease Control and Prevention declared last week that flu activity nationwide had reached epidemic levels.

Shortly after the CDC announcement, Dr. Julia Morita, medical director of the Chicago Department of Public Health, answered more than a dozen questions about the flu season on Twitter via the hashtag #FluChicago.

"Our goal is to provide relevant information as quickly as possible to as many people as possible," department spokesman Brian Richardson said. "In order to do that effectively today, social media has to play a part."

The mayor's office has also spread the word about the flu season online, creating an interactive map that shows where vaccines are available. Kevin Hauswirth, Chicago's first-ever social media director, said the city has shared the code behind its flu map with Boston, which declared a public health emergency Wednesday after an unprecedented spike in flu cases.

"We understand that those conversations are happening online, and the mayor's office should be a part of those conversations, especially when the health of the city is at stake," Hauswirth said.

The Twitter chat and flu map come amid several broader efforts to crowdsource flu data, some of which have been successful in sketching the contours of what local doctors agree is the worst season since the swine flu pandemic in 2009.

Flu Near You is a website that enables users to complete a weekly health survey and then displays on an interactive map where flu sufferers are located. More than 44,000 people were participating in Flu Near You as of Monday afternoon.

Nearly six weeks before the CDC issued a formal warning, the Baltimore-based startup Sickweather tweeted that "flu is a little early this year," linking to its barely 1-year-old website. Sickweather aggregates millions of flu-related mentions on Facebook and Twitter, filtering out those that are out of context, and plots them on an interactive map.

From August to October, co-founder Graham Dodge said he noticed a 70 percent increase in social media buzz about the flu compared with past data from Google Flu Trends, which tracks flu-related search terms, and the CDC. He called the advance warning a public service.

"We're actually taking that data and turning it around and giving it back to the users in a form that they can utilize," Dodge said.

Sickweather's early read on the flu season is not the only jump the Internet has gotten on the CDC. Google Flu Trends' algorithm produced a "strong correlation" with real-time flu activity in a Johns Hopkins Medicine study a year ago.

"Cues from social media are actually a robust way to know what's going on in the community," said Dr. Richard Rothman, who worked on the widely cited investigation with lead researcher Dugas.

Rothman and Dugas are now working on a model that uses both Google Flu Trends and more official data to predict flu prevalence in emergency rooms a week before it happens.

"You don't rely on just one tool," Dugas said, noting online indicators like Google Flu Trends are not "meant to be used entirely in isolation."

(c) 2013 Chicago Tribune Distributed by McClatchy-Tribune News Service.