What we know (and don't know) about Ebola - Alex Gendler

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The highly virulent Ebola virus has seen a few major outbreaks since it first appeared in 1976 -- with the worst epidemic occurring in 2014. How does the virus spread, and what exactly does it do to the body? Alex Gendler details what Ebola is and why it's so hard to study.

Lesson by Alex Gendler, animation by Andrew Foerster.

In the summer of 1976,

a mysterious epidemic
suddenly struck two central African towns,

killing the majority of its victims.

Medical researchers suspected

the deadly Marburg virus
to be the culprit.

But what they saw in microscope images
was an entirely new pathogen,

which would be named
after the nearby Ebola river.

Like yellow fever or dengue,

the disease caused by the Ebola virus
is a severe type of hemorrhagic fever.

It begins by attacking
the immune system's cells

and neutralizing its responses,

allowing the virus to proliferate.

Starting anywhere from two to twenty days
after contraction,

initial symptoms like high temperature,

aching,

and sore throat

resemble those of a typical flu,

but quickly escalate to vomiting,

rashes,

and diarrhea.

And as the virus spreads,

it invades the lymph nodes
and vital organs,

such as kidneys and liver,
causing them to lose function.

But the virus itself
is not what kills Ebola victims.

Instead, the mounting cell deaths
trigger an immune system overload,

known as a cytokine storm,

an explosion of immune responses
that damages blood vessels,

causing both internal and external bleeding.

The excessive fluid loss
and resulting complications

can be fatal within six to sixteen days
of the first symptoms,

though proper care and rehydration therapy

can significantly reduce
mortality rates in patients.

Fortunately,
while Ebola is highly virulent,

several factors limit its contagiousness.

Unlike viruses that proliferate through
small, airborne particles,

Ebola only exists in bodily fluids,

such as saliva,

blood,

mucus,

vomit,

or feces.

In order to spread,

these must be transmitted from
an infected person into another's body

through passageways such as the eyes,
mouth, or nose.

And because the disease's severity

increases directly along
with the viral load,

even an infected person
is unlikely to be contagious

until they have begun to show symptoms.

While Ebola has been shown
to survive on surfaces for several hours,

and transmission through sneezing
or coughing is theoretically possible,

virtually all known cases of contraction
have been through direct contact

with the severely ill,

with the greatest risk
posed to medical workers

and friends or relatives of the victims.

This is why,
despite its horrifying effects,

Ebola has been far less deadly overall
than more common infections,

such as measles,

malaria,

or even influenza.

Once an outbreak has been contained,

the virus does not exist
in the human population

until the next outbreak begins.

But while this is undoubtedly a good thing,

it also makes Ebola difficult to study.

Scientists believe fruit bats
to be its natural carriers,

but just how it is transmitted to humans
remains unknown.

Furthermore, many of the countries
where Ebola outbreaks occur

suffer from poor infrastructure and sanitation,

which enables the disease to spread.

And the poverty of these regions,

combined with the relatively low amount
of overall cases

means there is little economic incentive
for drug companies to invest in research.

Though some experimental medicines
have shown promise,

and governments are funding development
of a vaccine,

as of 2014,

the only widespread and effective
solutions to an Ebola outbreak remain

isolation,

sanitation,

and information.