Twitter kept up with Haiti cholera outbreak

Social media can track disease spread even in poorest countries

Twitter, blogs and other social media can be powerful tools for tracking infectious diseases as they spread in poor countries with weak institutions and infrastructure conclude researchers who followed social media during Haiti’s post-earthquake cholera outbreak in 2010.

Twitter posts and news about cholera gathered from the Internet in the first 100 days of the outbreak tracked closely with official data reported from hospital and clinics. But the social media data were available almost instantly, instead of days to weeks after the fact. Mining such informal news sources could allow for speedier interventions with vaccines or antibiotics, the researchers report in the January issue of the American Journal of Tropical Medicine and Hygiene.

“There’s very useful information in some of these nontraditional sources,” says Philip Polgreen, an expert in bioinformatics and epidemiology at the University of Iowa, who was not involved with the study. Polgreen and others have shown that Twitter and other online sources can provide meaningful information about outbreaks of diseases such as H1N1 and swine flu. But the new work establishes that the approach is useful for tracking a disease that emerges in the unsafe living conditions that often follow a disaster, says Polgreen.

The water supply and sewer infrastructure in Haiti deteriorated so dramatically after the devastating January 2010 earthquake that the country experienced a cholera outbreak for the first time in a century. The waterborne disease killed more than 6,500 people and sickened nearly half a million.

But while the country’s sanitary infrastructure is lacking, an estimated 3.5 million of Haiti’s 10 million inhabitants have cell phones, which can be used to send 140-character Twitter posts, known as tweets, out onto the Internet.  Researchers from Harvard Medical School, Children’s Hospital Boston and McGill University in Montreal collected 188,819 tweets that contained or were tagged with the word cholera during the first 100 days of the cholera outbreak — from October 20, 2010, the date of the first official cholera hospitalization, to January 28, 2011.

The team’s analysis suggests the social tool provides a good measure of the disease’s spread. Early posts to Twitter included “Sitting w/a father who just lost his 7-year old to cholera. Reality still has not hit,” and “My visit to Saint Nicolas hospital in Saint Marc, As Haiti is still fighting Cholera.” As with data from online news sources and the official health data, the tweeted cholera chatter spiked at the start of the outbreak and during the increase of cases seen when Hurricane Tomas came close to Haiti on November 5.

The researchers compared the tweets to data from HealthMap, a disease-tracking tool that mines Internet news stories, blogs and discussion groups and lets the public report illness by cell phone. Both the Twitter and HealthMap data corresponded to official data from the Haitian Ministry of Public Health.

“Official sources of data are better validated, but on the downside they are going to take time,” says biomedical engineer Rumi Chunara of Harvard Medical School and Children’s Hospital Boston, who led the new work. “Looking back, to find it correlated so well, it’s cool.” 

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