at once, from tracing infected contacts and encouraging changes in
behaviour to opening treatment centres and conducting safe burials.
What effect did international efforts actually have?
Using a mathematical model of Ebola transmission, our group
estimated that the introduction of additional treatment beds – which
isolated cases from the community and thereby reduced transmission
- prevented around 60,000 Ebola cases in Sierra Leone between
September 2014 and February 2015. In some districts, we found that
the expansion of treatment centres could explain the entire outbreak
decline; in other areas, there was evidence of an additional reduction
in transmission in the community. This could have reflected other
local and international control efforts, or perhaps changes in
behaviour that were occurring anyway.[69]
Historical Ebola outbreaks have shown how important behaviour
changes can be for outbreak control. When the first reported outbreak
of Ebola started in the village of Yambuku, Zaire (now the Democratic
Republic of the Congo) in 1976, the infection sparked in a small local
hospital before spreading to the community. Based on archive data
from the original outbreak investigation, my colleagues and I
estimated that the transmission rate in the community declined
sharply a few weeks into the outbreak.[70] Much of the decline came
before the hospital closed and before the international teams arrived.
‘The communities where the outbreak continued to spread developed
their own form of social distancing,’ recalled epidemiologist David
Heymann, who was part of the investigation.[71] Without doubt, the
international response to Ebola in late 2014 and early 2015 helped
prevent cases in West Africa. But at the same time, foreign
organisations should be cautious about claiming too much credit for
the decline of such outbreaks.
D in producing forecasts, there is a
large demand for them. Whether we’re looking at the spread of
infectious diseases or crime, governments and other organisations
need evidence to base their future policies on. So how can we
improve outbreak forecasts?