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 Concern that the virus could gain capability to transmit through the
air - creating a nightmare scenario of the disease being able to
spread like a flu pandemic, killing millions - was fueled by a top
infectious disease expert in the United States.
Michael Osterholm, director of the Center for Infectious Disease
Research and Policy at the University of Minnesota, said in an
opinion article he believed the risk of airborne Ebola is real, and
warned: "Until we consider it, the world will not be prepared to do
what is necessary to end the epidemic."
Yet many other virus and infectious disease specialists say that
while the prospect of an airborne Ebola virus is not impossible, it
is extremely remote.
"This is way down on the list of possible futures for Ebola and in
all probability will never happen," said Ian Jones, a virologist at
Britain's University of Reading.
Ebola is contagious, but spreads via direct contact with the bodily
fluids of an infected person, such as their blood, faeces or vomit.
The virus has infected 5,357 people in West Africa this year,
killing 2,630 of them, in the worst Ebola epidemic the world has
seen. [ID:nL6N0RJ3N0]
Ben Neuman, a Reading virologist who has been monitoring the Ebola
epidemic since it began in Guinea, noted that under carefully
controlled laboratory conditions, scientists have shown it is
feasible to make Ebola transmit through air, but added: "So far
there is no solid evidence that it actually happens out there in the
real world."
"One clue is how slow the virus is spreading," he told Reuters.
"Compared to this Ebola outbreak, the H1N1 swine flu had already
spread to an estimated 10,000 times as many people in its first 10
months."
That's not to say the Ebola virus isn't mutating. It is, rapidly,
all the time.
In a study published in the journal Science late last month, a team
of researchers sequenced 99 Ebola virus genomes isolated from blood
samples of 78 patients in Sierra Leone -- one of the four countries
at the heart of the epidemic.
They found what they described as "a rapid accumulation of interhost
and intrahost genetic variation" -- in other words, a large number
of frequent changes in the virus -- even in the initial few weeks of
the outbreak.
"SLOPPY" RNA VIRUS
Unlike some other nasty viruses such us smallpox and hepatitis B,
Ebola, like HIV and flu, is an RNA virus -- one whose genetic
material is contained in ribonucleic acid (RNA) rather than
deoxyribonucleic acid (DNA).
RNA viruses are renowned for their rapidly changing nature and are
often described by virologists as "sloppy" viruses because when they
replicate, they make copies of themselves that are full of errors.
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But most of these mistakes, or changes, are just "irrelevant
mutations", explained Anthony Fauci of the United States National
Institute of Allergy and Infectious Diseases.
Fauci told a U.S. senate hearing this week that the changes so far
observed in Ebola in this outbreak, while prolific, were generally
"not associated with a biological change or a biological function"
of the virus, meaning they were highly unlikely to give it an
entirely new skill, such as the ability to transmit in droplets in
the air.
"It is an unusual situation where a mutation would completely change
the way a virus is transmitted," Fauci said. "It's not impossible,
but it would be unlikely."
Jones added that the so-called tropism of the Ebola virus -- the
tissue it prefers to infect -- is the vasculature, not the airway
surfaces.
"As a result it is not in the right place to make the leap to a new
transmission route," he told Reuters. "In fact very few viruses do
this. Most stay in the niche they have established over evolutionary
time."
Experts stress, however, that keeping close tabs on the mutations in
the Ebola virus is vitally important, particularly for those working
on developing potential drugs to treat the infection, or vaccines to
prevent it.
The researchers who sequenced the Ebola genomes and published their
findings in Science said many of the mutations they found had
altered protein sequences or other biologically meaningful targets
within the virus.
"They should be monitored for impact on diagnostics, vaccines, and
therapies critical to outbreak response," they wrote.
(Reporting by Kate Kelland; Editing by Will Waterman)
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