Ebola Outbreak May be Out of Proportion: Model Can No Longer Predict Its Unprecedented Spread

Could the Ebola outbreak be all out of proportion? Scientists have found that a mathematical model that replicates Ebola outbreaks can no longer be used to predict the eventual scale of the current epidemic, which means that researchers may need to take another look at Ebola's spread.

"If we analyze the data from past outbreaks we are able to design a model that works for the recorded cases of the virus spreading and can successfully replicate their eventual size," said Thomas House, a researcher who incorporated data from past outbreaks into a model, in a news release. "The current outbreak does not fit this previous pattern and, as a result, we are not in a position to provide an accurate prediction of the current outbreak."

The spread of the virus largely depends on chance events. Looking at past Ebola outbreaks, you can predict their overall size based on modeling chance events that are known to be important when the numbers of cases of infection are small and spread is being controlled. These chance events can include a person's location when they are most infectious, whether they are alone when they're ill and travel patterns. Yet it seems as if the latest outbreak doesn't completely follow past chance events-such as severity.

"With the current situation we are seeing something that defies this previous pattern of outbreak severity," said House. "As the current outbreak becomes more severe, it is less and less likely that it is a chance event and more likely that something more fundamental has changed."

So what might be causing the unprecedented nature of the current outbreak? House may have an explanation. He argues that there could be a range of factors that lead it to be on a different scale to previous cases, such as the mutation of the virus, changes in social contact patterns or a combination of these and other factors.

"Since we are not in a position to quantify the eventful scale of this unprecedented outbreak, the conclusion from this study is not to be complacent but to mobilize resources to combate the disease," said House.

The findings are published in the journal eLife.