Most of the people infected with Ebola in the West Africa epidemic that began in 2014 got sick through contact with a small number of "superspreaders" with the disease, researchers said Monday.
The study in the Proceedings of the National Academy of Sciences shows such "superspreaders" can be extremely dangerous when it comes to infectious disease outbreaks.
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.
"We now see the role of superspreaders as larger than initially suspected," said co-author Benjamin Dalziel, an assistant professor of population biology in the College of Science at Oregon State University.
"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 center."
At the time, researchers counted cases according to those seen in medical centers, but they later realized these were a small fraction of the total.
"There wasn't a lot of transmission once people reached hospitals and care centers," said Dalziel.
"In our analysis we were able to see a web of transmission that would often track back to a community-based superspreader."
In fact, 61 percent of those infected with the disease caught it from people accounting for just three percent of those who got sick, the researchers said.
The study included 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.
If superspreading had been completely under control about two-thirds of Ebola cases could have been avoided, the report said.
Superspreaders have also played a role in the epidemic of severe acute respiratory syndrome, or SARS, in 2003 and Middle East respiratory syndrome in 2012.
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