EBOLA OUTBREAK OUT OF ALL PROPORTION AND SEVERITY CANNOT BE PREDICTED
A mathematical model
that replicates Ebola outbreaks can no longer be used to ascertain the eventual
scale of the current epidemic, finds research conducted by the University of
Warwick
Dr Thomas House, of
the University’s Warwick Mathematics Institute, developed a model that
incorporated data from past outbreaks that successfully replicated their
eventual scale.
The research, titled "Epidemiological
Dynamics of Ebola Outbreaks" and published by eLife, shows
that when applying the available data from the ongoing 2014 outbreak to the
model that it is, according to Dr House, “out of all proportion and on an
unprecedented scale when compared to previous outbreaks”.
Dr House commented:
“If we analyse 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. 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”.
Chance events, Dr
House argues, are an essential factor in the spread of Ebola and many other
contagious diseases. “If we look at past Ebola outbreaks there is an
identifiable way of predicting their overall size based on modelling chance
events that are known to be important when the numbers of cases of infection
are small and the spread is close to being controlled”.
Chance events can
include a person’s location when they are most infectious, whether they are
alone when ill, the travel patterns of those with whom they come into contact
or whether they are close to adequate medical assistance.
The Warwick model
successfully replicated the eventual scale of past outbreaks by analysing two
key chance events: the initial number of people and the level of infectiousness
once an epidemic is underway.
“With the
current situation we are seeing something that defies this previous pattern of
outbreak severity. 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”, says Dr House.
Discussing possible
causes for the unprecedented nature of the current outbreak, Dr House argues
that there could be a range of factors that lead it to be on a different scale
to previous cases; “This could be as a result of a number of different factors:
mutation of virus, changes in social contact patterns or some combination of
these with other factors. It is implausible to explain the current situation
solely through a particularly severe outbreak within the previously observed
pattern”.
In light of the
research findings and the United Nations calling for a further $1bn USD to
tackle the current outbreak, Dr House says that “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 mobilise resources to combat the
disease.”
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