MS Risk Blog

“Superspreaders” Behind Ebola Outbreak in West Africa

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Researchers reported last month that most of the people infected with Ebola in the West Africa epidemic, which began in 2014, got sick through contact with a small number of “superspreaders” with the disease. The West African Ebola epidemic was the largest in history and killed more than 11,300 people, with many of the cases involving people infected while caring for a sick person or burying a body.

The study in the Proceedings of the National Academy of Sciences indicates that such “superspreaders” can be extremely dangerous when it comes to infectious disease outbreaks. According to co-author Benjamin Dalziel, an assistant professor of population biology in the college of Science at Oregon State University, “we now see the role of superspreaders as larger than initially suspected,” adding “it was the cases you didn’t see that really drove the epidemic, particularly people who died at home, without making it to a care centre.”

At the time, researches counted cases according to those seen in medical centres, however they later realized that these were a small fraction of the total. According to Dalziel, “there wasn’t a lot of transmission once people reached hospitals and care centres,” adding “in our analysis we were able to see a web of transmission that would often track back to a community-based superspreader.”

Researchers are now reporting that 61 percent of those infected with the disease caught it from people accounting for just three percent of those who got sick. The report went on to say that if superspreading had been completely under control, then about two-thirds of Ebola cases could have been avoided.

Superspreaders have also played a role in the epidemic of severe acute respiratory syndrome (SARS) in 2003 and Middle East respiratory Syndrome in 2012.

The study involved researchers from Princeton University, Oregon State University, the London School of Hygiene and Tropical Medicine, the International Federation of Red Cross and Red Crescent Societies, the Imperial College London and the US National Institutes of Health.