DAVID GREENE, host:
Of course, any natural disaster can teach us lessons. And certainly that's been true in Haiti for the past year and a half. The earthquake that hit the country in January of 2010 killed more than 300,000 people and left a million people homeless. Later in the year, a cholera epidemic swept through parts of the country.
In an extraordinary experiment, health workers and a cell phone company teamed up to track quake refugees, as well as people who are possibly carrying cholera. As NPR's Christopher Joyce reports, the effort helped target relief and anticipate the spread of the epidemic.
CHRISTOPHER JOYCE: The one, two punch of earthquake and cholera threatened to decimate the crowded capital city of Port-au-Prince. The quake drove a million survivors into tent camps with little sanitation or clean water. Months later, cholera emerged in a northern province and threatened to invade the city.
So authorities sent radio and television celebrities into the camps like this one, on a highway median strip. The visitors led children in song.
(Soundbite of singing)
JOYCE: The message?
Unidentified Man: (French language spoken)
JOYCE: An epidemic of cholera threatened. The songs said, Wash your hands, drink clean water, report diarrhea.
But while celebrities sang, international organizations were doing something rather different - tracking people in and out of the city, and across the northern provinces where cholera was spreading. They did it by tracking calls back to the SIM cards in peoples' cell phones.
Linus Bengtsson, a public health expert at Sweden's Karolinska Institute, says the tracking started before the epidemic, just after the earthquake.
LINUS BENGTSSON (Disaster Medicine, Karolinska Institute): When people start to move around, let's say as they often do after a disaster, it's very difficult to know where to deliver supplies.
JOYCE: Watching the tragedy unfold from Sweden, Bengtsson knew that cell phone companies like Digicell in Haiti keep data on calls for billing purposes. And he knew the company could trace each call in their records to the closest cell tower, sometimes within a couple of blocks of the phone.
Bengtsson reached out to public health specialist Richard Garfield of Columbia University. At the time, Garfield had been working at Haiti's national hospital.
Professor RICHARD GARFIELD (School of Nursing, Columbia University): So I went over and knocked at the door of Digicell.
JOYCE: What did they say?
Prof. GARFIELD: They were quite receptive conceptually to the idea.
JOYCE: The idea being follow quake refugees to find out where people are in need. The team followed almost two million phones before and after the quake. They found that within three weeks, more than 600,000 people fled Port-au-Prince. And they knew where they went.
Health officials were somewhat relieved at the news. It took pressure off aid groups inside the capital. But the relief didn't last long; the cell phones showed the refugees didn't stay in the countryside.
Prof. GARFIELD: They were already producing all the food they can, in those depleted lands, and there was just a very temporary capacity to hold those people. So people kept moving around, which often occurs in mass disasters, and quickly came back to Port-au-Prince as soon as they could.
JOYCE: Then cholera struck in northern Haiti. So the Karolinska team tracked cell phone owners there, people who fled the epidemic area. Where they went, the disease could follow. Authorities needed to know where to send medical aid - and it worked.
Prof. GARFIELD: The second wave of cases did appear exactly in the areas where most of the population were moving to, who were moving out of the cholera zone.
JOYCE: The team never knew the names of phone owners. But health authorities could still send the phone owners health advice via voice-mail and text.
Sabina Carlson, from the International Organization for Migration, recites one of the messages that went out.
SABINA CARLSON (Coordinator, Community Outreach, International Organization for Migration): (French language spoken)
So, which is, you need to breast-feed young children even if they have diarrhea.
JOYCE: Scientists who track diseases, like malaria expert Andrew Tatem, of the University of Florida, say the technique has great promise.
Professor ANDREW TATEM (Emerging Pathogens Institute, University of Florida): I think it's incredibly beneficial. I think we're kind of seeing a glimpse of the future of gathering information for disaster management.
JOYCE: The results of the project appear in the journal "PLOS Medicine."
Christopher Joyce, NPR News.
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