Why Ebola Hasn't Been Cured Yet

Ebola first appeared more than three decades
ago, but there is still no cure or specific
treatment for the disease, in part because the
dangerous nature of the virus makes it difficult
to study, experts say.
People with Ebola are treated with only general
therapies meant to support the ill patient. They
might be given fluids (Ebola patients are
frequently dehydrated), or treatments aimed at
maintaining blood pressure and oxygen levels,
and treating infections if they develop, according
to the Centers for Disease Control and
Prevention.
So why aren't there more specific treatments for
Ebola?
Part of the reason is that Ebola is caused by a
virus, rather than bacteria, and researchers in
general have had a harder time developing
treatments for viral diseases, compared with
bacterial diseases, said Derek Gatherer, a
bioinformatics researcher at Lancaster
University in the United Kingdom who studies
virus genetics and evolution.
"Antiviral therapy has lagged behind
antibacterial therapy for decades," Gatherer
said.
That's because viruses are small molecules that
produce only a handful of proteins, so there are
fewer "targets" for treatment, Gatherer said. For
this same reason, it has been hard to develop a
vaccine against Ebola; a person's immune
system (which is primed by vaccines) has a
small target, Gatherer said.
Ebola viruses also evolve quite quickly, so it's
not clear whether a vaccine developed today
would protect against future outbreaks, he said.
(Ebola viruses belong to a family of viruses
called Filoviridae, and there are five known
species of Ebola virus.)
And because the virus is so dangerous in some
outbreaks, the mortality rate has been as high
as 90 percent researchers must work with the
virus in special facilities with high-level safety
precautions, which limits the number of
experiments that can be done.
"There's only a handful of places in the world
were you can actually do Ebola
experimentation," Gatherer said. Ebola viruses
require a "biosafety level 4" laboratory the
highest level of protection.
In addition, relatively few people have ever been
infected with Ebola, and even fewer have
survived, thus making it hard to study the virus
in people or examine whether there are certain
biological factors that help people survive,
Gatherer said.
Ebola first appeared in 1976, in outbreaks in the
Democratic Republic of Congo and Sudan. The
origin of the virus is not known, but it is
thought to reside in bats.
People become infected with Ebola through
close contact with infected animals, and the
virus spreads person-to-person through contact
with bodily fluids, such as blood or secretions,
according to WHO. Symptoms include fever,
muscle pain and headache, followed by
vomiting, diarrhea, rash and, in some cases,
internal and external bleeding, WHO says.
The Ebola virus attacks immune cells, and can
cause the immune system to run out of control
and release a "storm" of inflammatory
molecules, which cause tiny blood vessels to
burst, Gatherer said. This blood-vessel damage
can cause blood pressure to drop, and lead to
multiple-organ failure, Gatherer said.
Some potential Ebola treatments show promise
in animal models, including compounds that
interfere with the way the virus replicates. Other
experimental treatments aim to prevent the
virus from entering cells, by blocking the
proteins on the surface of cells to which the
virus binds.
Another therapy in the works involves injecting
mice with parts of the virus and using their
antibodies to treat infection. In a 2012 study,
four monkeys with Ebola survived the infection
when they were given a combination of these
antibodies one day after infection