Twitter Tracks Cholera Outbreaks Faster Than Health Authorities

Getting a jump of two weeks on an infectious disease can mean the difference between life and death, between containment and an epidemic. Now researchers have shown that, for the 2010 cholera epidemic in Haiti, social media like Twitter can track outbreaks as much as two weeks sooner than official health reports, especially when used by people with mobile phones.

“The faster we know where a disease is spreading, the faster we can put in control measures,” said Rumi Chunara, a research fellow at Children’s Hospital Boston and Harvard Medical School. “Do we need to vaccinate people? Distribute antibiotics? Clean water?” Ms. Chunara and two colleagues described the public-health advantages of social media in an article published on Monday in The American Journal of Tropical Medicine and Hygiene.

Since cholera began raging across Haiti in 2010, following a devastating earthquake and hurricane, there have been more than 380,000 cases and more than 5,000 deaths. The health ministry in Haiti tracked the spread of the epidemic in standard fashion: It sent out health-care workers, collected reports from hospitals, and used the reports to direct resources. Ms. Chunara and her co-workers compared those reports with Twitter feeds that mentioned the word “cholera” during that time, and with reports from a Children’s Hospital project called HealthMap, which identifies disease hot spots through news reports, blogs, and discussion groups that mention the disease.

The social media matched the official reports very closely right at the start of the outbreak, in October 2010, and right after another surge when the hurricane hit, in early November. But the reports were ahead of the official records by two weeks. And with Twitter in particular, they identified the geographic locations of the cases “because a lot of people were Tweeting from their phones, right where they saw patients” in villages, Ms. Chunara said. Not all cholera patients go to hospitals to be counted officially, she noted.

Social media are not a magic bullet for a crisis, however, and that was also evident in Haiti when the earthquake hit. Aid agencies relied on text messages from cellphones and crowd-sourced maps to direct rescue workers. One of those “crisis maps,” called Ushahidi, collected calls for help from across the island and used them to identify areas where the need for help was greatest and most urgent. The approach worked well at many times but not always smoothly: A report on the Haiti experience by the Knight Foundation noted that volunteers and professional aid workers did not share the same operating procedures, which “complicated efforts on the ground.”

So disease trackers now have to show that social media pinpoint disease outbreaks as they are happening, not just in an after-the-fact experiment like this one. The World Health Organization is currently monitoring clusters of yellow fever in Senegal, bird flu in Egypt, and lead poisoning in Nigeria. And malaria epidemics kill more than 100,000 people worldwide every year. So unfortunately there will be no shortage of opportunities for testing the new strategy.