What can we do to stop the Ebola spread?

How much of a threat is Ebola, and what can we do to stop it? We put your questions to Dr. Chris Smith.
14 October 2014

Interview with 

Dr Chris Smith, Cambridge University


So far at least 8000 people have been infected with Ebola, and half of those have died; it's spreading at an exponential rate and it's on the move...

Ebola cases have now been confirmed in Europe and America. A nurse at a Madrid hospital treating two infected missionaries herself contracted the disease, while in Dallas, a man who caught the virus in his native Liberia has since died. 

So how much of a threat is ebola, and what can we do to stop it. We asked your questions to Chris, who is a consultant virologist...

Kat -   So Chris, give us a quick top down.  What is Ebola?  Where did it come from and how is it spreading?  Should we just be panicking and putting on masks everywhere?

Chris -  Ebola is a virus, Kat.  It has been around since the later 1970s.  1976 was when the first human case was recorded but there were certainly cases before that.  Periodically, it's caused little outbreaks of a few hundred people at a time.  So, this outbreak which is happening ever since probably we think December last year, the index case was a young 2-year-old boy in Sierra Leone last December based on genetic studies.  This current outbreak will therefore be at least equivalent to all of the deaths of all of the previous outbreaks of Ebola in the last 40 years.  So in other words, it's a massive departure and it's very unusual.

Kat -  Now, I've heard people describe Ebola as a zoonotic virus.  What does this mean?  Does that reflect where it's coming from?

Chris -  Yes.  So, about 75% of what we call emerging infections which are infections that haven't previously is circulated in humans, but have now got into humans.  About 3 quarters of them come from an animal reservoir.  In other words, they're naturally an infection of a wild animal and through some mechanism which can vary, they get out of that wild animal and they jump into humans.  Now because they're well adapted to living in a wild animal, they're not well adapted - these viruses - to living in humans.  They tend to make us much sicker than the wild animal host which is why the animal that naturally carries Ebola which is some species of fruit bats, they can carry it without becoming unwell.  But when it gets into a human, it's a massive case of overkill and about 70% to 90% of people who become infected will die.

Kat -  Now, we've had a couple of questions in on Twitter.  We have something from fullcircle man who says, "Are there more virulent zoonotic viruses out there in nature that remain undiscovered and should we worry about them?"

Chris -  Well, we don't know yet, but it's a very good question.  The thing is that if you look at what's probably provoked the present Ebola outbreak, a paper from Simon Hay and his colleagues at the University of Oxford which was published last month in eLife showed that the mechanism is almost certainly down to population and communications.  We've now got 300% plus more people living in the areas where the Ebola outbreak has happened than historically.  There are much better roads in communications and this means that people are more likely to come into contact with wildlife and once they catch an infection, they're much more mobile, so they're more likely to spread it.  This also means that if there are other nasty viruses lurking out there, we're more likely to come into contact with them as the population grows and there's more pressure on the environment to build houses and feed people.  So, farmers move into virgin rainforest, houses get built on virgin rainforest, and so on.  So, we don't know what's lurking out there yet.  But if you look at the last 10 years or so, we've had the SARS epidemic and that became a pandemic, and SARS was a natural infection of bats in China.  We've also had an outbreak a bit before that of a disease called Nipah virus which again was a bat virus that got into pig farmers in Malaysia.  So, who knows what's lurking out there but we really have to be careful and all actually comes down to population.

Kat -  I remember the MERS one.  I think that's a camel one.  In this month's Naked Genetics podcast that's coming out on Tuesday, I'm looking at the bat flu virus genes that researchers have been studying.  A couple more questions.  We've got Stuart Degrut says, "What about the outbreak in Europe?  Isn't it pretty hard to get infected with Ebola?  How are these healthcare workers becoming infected here in Europe and America?"

Chris -  If you look at the rate of infectivity of things like Ebola, it only takes between 1 and 10 virus particles to infect a victim.  But that does require close contact.  You need to get the virus into a mucus membrane.  In other words, around your eyes, into your mouth - that kind of thing - or into damage or a breach or abrasion into your skin.  So, if we look at the cases that have happened in developed countries, the nurse in Spain who caught it thinks that despite the fact she was wearing protective gear, there was probably enough virus because a person who's infected with Ebola will therefore have effectively an entire world infecting dose inside them because they will have billions of viruses in them and all the secretions that leave the body, all body fluids including vomit, diarrhoea and so on, which are symptoms of Ebola.  If that gets on to a piece of protective clothing, but then you touch the piece of protective clothing, the virus can go onto your skin and if you then rub that into a mucus membrane such as into your eye, put your fingers in your mouth, or you have a small cut or abrasion to the skin, it can go in and then it can infect you.

Kat -  It is absolutely terrifying to me anyway.  A question from Matias Tula, "How far are we from a vaccine or an effective treatment - 6 months, a year?"  Where are we going to be with this because this does seem like a crisis basically?

Chris -  There are two vaccines currently being trialled.  One is from GlaxoSmithKline.  They're actually developing this and doing this in a human trial in Oxford.  Animal test of the same platform or technology had been very effective.  What they're doing is they've taken a virus that normally causes the cold in chimpanzees.  They have stopped the virus from growing.  So basically, it can only act as a sort of virus coat to carry Ebola coat genes into a person.  This shows the immune system what Ebola looks like, making them make antibodies to Ebola.  They have now got that going into people as a phase I trial.  We'll find out whether that works.  It does work very well in animals.  There's a similar technology being done by a company in America called NewLink and it's been developed by Canadian academics, NewLink developing it.  But both say it will take several years before we a.) know how effective it is to get the right sorts of numbers, b.) to make enough of it to stem the current outbreak.  We're talking about needing probably a hundred thousand doses and we're nowhere near having that much yet.

Kat -  Well, you can read more about Ebola on our website that's https://www.thenakedscientists.com/articles.


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