The way people express their opinions and emotions on microblogging site Twitter may signal the rise of influenza, depression or other health issues in a specific area, an analysis of millions of anonymous tweets has revealed.

"Opinions and emotions are present in every tweet, regardless of whether the user is talking about their health," said lead author Svitlana Volkova, a data scientist at the US Department of Energy's Pacific Northwest National Laboratory (PNNL) in Washington."Like a digital heartbeat, we're finding how changes in this behaviour relate to health trends in a community," Volkova added, in the report published in the journal EPJ Data Science.It takes health workers weeks to discover influenza trends the traditional way: By monitoring how many sick people visit clinics. However, by discovering trends in real time, social media could be the game-changing solution public health workers have been looking for, the researchers said.

To truly tap this source of public data, researchers at PNNL sought to understand patterns of how people behave differently on social media when they are sick.
Thus, the team analysed 171 million tweets from users associated with the US military to determine if the opinions and emotions they express reflect visits to the doctor for influenza-like illnesses. They compared military and civilian users from 25 US and six international locations to see if this pattern varies based on location or military affiliation.They found that how people behaves varies significantly by location and group.Further, neutral opinions and sadness were expressed most during high influenza-like illness periods. During low illness periods, positive opinion, anger, and surprise were expressed more.