Tracking swine flu via Twitter

HealthMap, the online disease-surveillance system created by Children's Hospital Boston researchers, is getting faster. Now the real-time disease tracker is posting Twitter messages on the current swine flu outbreak.

HealthMap already bolsters official reports with the early warning that Internet searches, chat rooms, or news stories can give about emerging infectious diseases. Sometimes these unofficial sources predate expert alerts, a potentially important asset when diseases can quickly circle the globe via international air travel.

A month ago HealthMap added Twitter to the mix. So far the short-message service has grown from 50 to 1,800 users, serving up "tweets" about cases from Lowell to New Zealand.

"I think that probably a lot of users coming to the site were specifically looking for that type of information -- show me a list of the latest on this outbreak," HealthMap co-founder Clark Freifeld said in an interview. "Twitter is ready to do that."

HealthMap itself is drawing 50,000 unique visitors a day, a level it used to reach in a month. Regular users include the World Health Organization, the US Centers for Disease Control, and the European Centre for Disease Prevention and Control.

Informatics experts John Brownstein and Freifeld founded the service after the SARS outbreak in 2002. In last month's Canadian Medical Association Journal, Brownstein reported that Google searches for a food-borne disease spiked almost a month before the official announcement of an outbreak linked to a Canadian deli meat plant, providing an early warning of the fatal outbreak.

When traffic about swine flu exploded on HealthMap on Saturday, they tracked its earliest mention back to a local newspaper in Veracruz, Mexico, on April 1.

"The reality is we are combing through hundreds of outbreaks at the same time," Brownstein said. "Avian flu in Egypt was a major concern then so we were following it more closely."

More cases emerged through the month, bringing swine flu into the same WHO category as avian flu and SARS: outbreak of international significance.