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In the summer of 1976,
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a mysterious epidemic
suddenly struck two central African towns,
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killing the majority of its victims.
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Medical researchers suspected
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the deadly Marburg virus
to be the culprit.
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But what they saw in microscope images
was an entirely new pathogen,
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which would be named
after the nearby Ebola river.
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Like yellow fever or dengue,
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the disease caused by the Ebola virus
is a severe type of hemorrhagic fever.
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It begins by attacking
the immune system's cells
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and neutralizing its responses,
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allowing the virus to proliferate.
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Starting anywhere from two to twenty days
after contraction,
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initial symptoms like high temperature,
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aching,
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and sore throat
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resemble those of a typical flu,
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but quickly escalate to vomiting,
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rashes,
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and diarrhea.
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And as the virus spreads,
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it invades the lymph nodes
and vital organs,
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such as kidneys and liver,
causing them to lose function.
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But the virus itself
is not what kills Ebola victims.
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Instead, the mounting cell deaths
trigger an immune system overload,
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known as a cytokine storm,
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an explosion of immune responses
that damages blood vessels,
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causing both internal and external bleeding.
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The excessive fluid loss
and resulting complications
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can be fatal within six to sixteen days
of the first symptoms,
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though proper care and rehydration therapy
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can significantly reduce
mortality rates in patients.
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Fortunately,
while Ebola is highly virulent,
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several factors limit its contagiousness.
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Unlike viruses that proliferate through
small, airborne particles,
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Ebola only exists in bodily fluids,
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such as saliva,
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blood,
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mucus,
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vomit,
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or feces.
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In order to spread,
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these must be transmitted from
an infected person into another's body
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through passageways such as the eyes,
mouth, or nose.
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And because the disease's severity
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increases directly along
with the viral load,
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even an infected person
is unlikely to be contagious
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until they have begun to show symptoms.
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While Ebola has been shown
to survive on surfaces for several hours,
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and transmission through sneezing
or coughing is theoretically possible,
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virtually all known cases of contraction
have been through direct contact
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with the severely ill,
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with the greatest risk
posed to medical workers
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and friends or relatives of the victims.
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This is why,
despite its horrifying effects,
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Ebola has been far less deadly overall
than more common infections,
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such as measles,
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malaria,
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or even influenza.
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Once an outbreak has been contained,
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the virus does not exist
in the human population
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until the next outbreak begins.
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But while this is undoubtedly a good thing,
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it also makes Ebola difficult to study.
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Scientists believe fruit bats
to be its natural carriers,
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but just how it is transmitted to humans
remains unknown.
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Furthermore, many of the countries
where Ebola outbreaks occur
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suffer from poor infrastructure and sanitation,
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which enables the disease to spread.
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And the poverty of these regions,
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combined with the relatively low amount
of overall cases
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means there is little economic incentive
for drug companies to invest in research.
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Though some experimental medicines
have shown promise,
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and governments are funding development
of a vaccine,
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as of 2014,
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the only widespread and effective
solutions to an Ebola outbreak remain
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isolation,
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sanitation,
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and information.