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Record-breaking Ebola outbreak: phone data reconstruct first weeks of spread
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Confirmed infections of Bundibugyo Ebola have surpassed 10,000 in the DRC since May.Credit: Xinhua/Shutterstock
Epidemiologists have used mobile-phone data and test records to map the early spread of Ebola in the Democratic Republic of the Congo (DRC)1 weeks before the outbreak was declared. The authors say the study findings reveal how surveillance systems failed to detect signals of the disease early on and enabled it to spread rapidly.
It is now six months since the outbreak of the Bundibugyo strain of the virus was announced. The number of confirmed infections has risen to more than 10,000 and 5,198 people have died, making this the largest Bundibugyo outbreak so far. There are no licenced vaccines or approved treatments specifically for Bundibugyo, which has complicated efforts to control it.
The DRC declared the outbreak on 15 May after laboratory tests confirmed the first case, a person from Ituri province in the country’s northeast, was infected with the Bundibugyo strain. Around the same time, suspected cases were being reported in several DRC locations, including Mongbwalu, Rwampara, Bunia and Nyankunde in Ituri, and Butembo, Katwa and Goma in the neighbouring province of North Kivu. The World Health Organization declared the outbreak a public health emergency of international concern on 17 May, citing infections among health-care workers, the geographical spread of cases and clusters of undocumented deaths. Researchers strongly suspect that the virus had been spreading in the region months earlier.
To understand how the outbreak spread so quickly, the researchers looked at anonymized mobile-phone data to trace the movement of people between areas.
Although the first confirmed case was identified on 15 May, the study reports that the person had symptoms as early as 25 April.
The team found that people travelling out of Mongbwalu, Bunia and Rwampara between 24 April and 24 May helped to predict which health zones would report infections by 1 June. For instance, areas close to the initial centres were at greater risk of infections, the study found.
The risk of infections rose again in places 150–200 kilometres away from the initial outbreak centres because people travelled to larger towns and cities along established routes, says study co-author Pierre Akilimali, an epidemiologist at the National Institute of Public Health (INSP) in Kinshasa.
The authors say the findings show that people movement was a key driver of the rapid spread in the early phases of the outbreak.