A recent study from the University of Cambridge alleges that half of all Ebola outbreaks have gone unseen and unrecorded since the virus was first discovered in 1976.
While this supports advocates’ push for improved detection and rapid response to the disease, it also means the situation provides a more challenging landscape. That said, most of these unknown cases, according to Cambridge’s Emma Glennon, were small — they tended to be clusters of fewer than five people. In all, they likely represent more than 100 cases, though, and researchers estimate that there is a less than 10 percent chance of detecting isolated cases of Ebola. Glennon and her team are the first to estimate the true figures.
“Most times that Ebola has jumped from wildlife to people, this spillover event hasn’t been detected,” Glennon, from Cambridge’s Department of Veterinary Medicine, said. “Often, these initial cases don’t infect anyone else, but being able to find and control them locally is crucial because you never know which of these events will grow into full outbreaks.”
This is especially problematic, as Glennon noted that Ebola outbreaks are rarely found when they’re still manageable — something the current outbreak in the Democratic Republic of Congo stresses.
“But if an outbreak is detected early enough, we can prevent it spreading with targeted, low-tech interventions, such as isolating infected people and their contacts,” Glennon said.
The study results, which consisted of three independent datasets from the 2013-2016 Ebola epidemic in West Africa, were published in PLOS Neglected Tropical Diseases. They used simulations to determine how likely a spillover event was to end early or progress into an outbreak.