WASHINGTON — Whooping cough first sickened the Illinois high school cheerleaders. Then it struck the football players, the cross-country team, and the band.
As it spread within the Chicago suburb of McHenry County in late 2011, another outbreak took place — on social media. A small business called Sickweather LLC said it detected the online flare-up on Twitter and Facebook postings in early October that year. That’s about two weeks before local health officials issued a public statement.
Now, US agencies want to expand their use of social media to spot potential biological attacks and outbreaks of deadly infectious diseases, including the new H7N9 avian flu that has killed dozens of people in China.
‘‘That’s the Holy Grail,’’ said Mark Dredze, an assistant research professor at Johns Hopkins University in Baltimore and a Sickweather adviser. ‘‘We’d love these systems to tell us there’s a brand new disease and it’s going to be a big thing.’’
The online disease trackers have had mixed results, with academics criticizing a tool by Google, the world’s biggest Internet search engine, for overestimating the number of US influenza cases. The system, dubbed Google Flu Trends, relied on search terms. It was never intended to be used on its own, said Matt Mohebbi, a former company engineer who helped create the tool.
Kelly Mason, a Google spokeswoman, said the company is open to feedback on how it can refine Flu Trends to help estimate influenza levels and ‘‘complement existing surveillance systems.’’
Companies such as Sickweather and Boston-based Epidemico are trying to get past the noise on the Internet. They rely on computer algorithms to scan social media and news articles for references to diseases like ‘‘whooping cough.’’ They try to screen out unrelated posts that might use ‘‘sick’’ (when they mean cool or insane) or ‘‘Bieber fever’’ (obsessed with pop star Justin Bieber).
The work also involves humans, in case the filters don’t catch everything or the algorithms exaggerate illness reports.
‘‘The big advantage of social media is you can get a lot more data, and you can get it more quickly and more economically,’’ said Henry Niman, a biomedical researcher and president of Pittsburgh-based Recombinomics, which analyzes viral evolution and the spread of disease. ‘‘It is a matter of fine-tuning that data so you come up with results that are more reliable.’’
Social media may help the Centers for Disease Control and Prevention, part of the US Department of Health and Human Services, better spot outbreaks in smaller communities, said Matthew Biggerstaff, a CDC epidemiologist.
It held a contest this year in which 11 teams composed of academics and industry and health officials competed to develop the best way of using social media to predict the flu season, he said. The winner will be announced by June 20.
‘‘These digital surveillance tools can help you start picking up signals a little bit earlier,’’ Biggerstaff said. ‘‘They give you access to real-time information before it starts registering on our system.’’
CDC officials typically track flu by monitoring reports of doctor visits, hospitalizations, and deaths, he said.
Those reports may take a while to trickle in. On Dec. 3, 2012, the agency announced the flu season was off to an early start. Sickweather’s Twitter post arrived about six weeks earlier: ‘‘Oh, hello #Flu, you’re a little early this year.’’
In a separate effort, the Department of Health and Human Services sought guidance from businesses in February on how it could tap social media to keep tabs on H7N9 and the Middle East Respiratory Syndrome. The MERS virus has killed at least 86.
It’s looking for near real-time analysis of Twitter posts that might show developments in the two diseases. Such tools might have other applications, including alerting government officials when hospitals or nursing homes are evacuating patients in a disaster.
‘‘If there’s a reason for it, we can direct resources to a community in need,’’ said Kelly Bennett, a public health analyst for Health and Human Services.