Scientists tracking the Ebola outbreak in Guinea say the virus
has mutated. Researchers at
the Institute Pasteur in France, which first identified the outbreak last March,
are investigating whether it could have become more contagious. Continue...
More than 22,000
people have been infected with Ebola and 8,795 have died in Guinea, Sierra
Leone and Liberia.
Scientists are
starting to analyse hundreds of blood samples from Ebola patients in Guinea.
They are tracking how
the virus is changing and trying to establish whether it's able to jump more
easily from person to person
"We know the
virus is changing quite a lot," said human geneticist Dr Anavaj
Sakuntabhai.
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“Start Quote
A virus can change
itself to less deadly, but more contagious and that's something we are afraid
of”
Dr Anavaj SakuntabhaiGeneticist
"That's important
for diagnosing (new cases) and for treatment. We need to know how the virus (is
changing) to keep up with our enemy."
It's not unusual for
viruses to change over a period time. Ebola is an RNA virus - like HIV and
influenza - which have a high rate of mutation. That makes the virus more able
to adapt and raises the potential for it to become more contagious.
"We've now seen
several cases that don't have any symptoms at all, asymptomatic cases,"
said Anavaj Sakuntabhai.
"These people may
be the people who can spread the virus better, but we still don't know that
yet. A virus can change itself to less deadly, but more contagious and that's
something we are afraid of."
But Professor Jonathan
Ball, a virologist at the University of Nottingham, says it's still unclear
whether more people are actually not showing symptoms in this outbreak compared
with previous ones.
"We know
asymptomatic infections occur… but whether we are seeing more of it in the
current outbreak is difficult to ascertain," he said.
"It could simply
be a numbers game, that the more infection there is out in the wider
population, then obviously the more asymptomatic infections we are going to
see."
Another common concern
is that while the virus has more time and more "hosts" to develop in,
Ebola could mutate and eventually become airborne.
There is no evidence
to suggest that is happening, however. The virus is still only passed through
direct contact with infected people's body fluids.
"At the moment,
not enough has been done in terms of the evolution of the virus both
geographically and in the human body, so we have to learn more. But something
has shown that there are mutations," said Institut Pasteur virologist Noel
Tordo.
"For the moment
the way of transmission is still the same. You just have to avoid contact (with
a sick person)"
"But as a
scientist you can't predict it won't change. Maybe it will."
Researchers are using
a method called genetic sequencing to track changes in the genetic make-up of
the virus. So far they have analysed around 20 blood samples from Guinea.
Another 600 samples are being sent to the labs in the coming months.
A previous similar
study in Sierra Leone showed the Ebola virus mutated considerably in the first
24 days of the outbreak, according to the World Health Organization.
It said: "This
certainly does raise a lot of scientific questions about transmissibility,
response to vaccines and drugs, use of convalescent plasma.
"However, many
gene mutations may not have any impact on how the virus responds to drugs or
behaves in human populations."
'Global
problem'
The research in Paris
will also help give scientists a clearer insight into why some people survive
Ebola, and others don't. The survival rate of the current outbreak is around
40%.
It's hoped this will
help scientists developing vaccines to protect people against the virus.
Researchers at the
Institute Pasteur are currently developing two vaccines which they hope will be
in human trials by the end of the year.
One is a modification
of the widely used measles vaccine, where people are given a weakened and
harmless form of the virus which in turn triggers an immune response. That
response fights and defeats the disease if someone comes into contact with it.
The idea, if it proves
successful, would be that the vaccine would protect against both measles and
Ebola.
"We've
seen now this is a threat that can be quite large and can extend on a global
scale," said immunologist at the Institute, Professor James Di Santo.
"We've
learned this virus is not a problem of Africa, it's a problem for
everyone."
He
added: "This particular outbreak may wane and go away, but we're going to
have another infectious outbreak at some point, because the places where the
virus hides in nature,
for example in small animals, is still a threat for humans in the future.
"The
best type of response we can think of… is to have vaccination of global
populations."
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