Avian Flu: What it is & where it comes from

克里斯- We've heard a little bit from Paul Digard about how flu is a virus. But could you just crystallise for us, what actually is the flu and where does it come from?

John - Well we can start with what it looks like, which is a football with lots of spikes sticking out around the outside. I like your idea of an escape kit, because the virus does have an escape kit and it needs it too. One of those spikes on the outside of the football is a mushroom shaped thing and that's called a neuraminidase, and that helps the virus chop its way through the layer of snot, as it were, and this is a very very very important layer. In fact, we put a lot of hope in this layer if the virus actually comes on the scene. The new drugs against flu, the ones we will be depending on, they're also targeted against this mushroom as well, so it's a pretty important part of the virus.

克里斯- Where did it come from in the first place?

John - We think the virus came from birds and that flu actually is a bird virus. Ten or eleven thousand years ago when Cambridge still had metres of ice on it, there weren't many humans around but there were plenty of birds. A thousand years later, there were maybe 20, 30 or 40 humans here, and then from then on, viruses like influenza which need a person to person transmission, they could spread. It's at that stage that we think the virus did a leap out of birds and into humans. Ever since, the birds such as ducks and geese have been the reservoir and we have also had the virus evolving with us. That's the position we're in at the moment. The question is whether a new virus is going to jump out of the reservoir and catch us all unawares.

克里斯- What stops it doing that anyway? Presumably it's because there are now two types of virus: bird types and human types that it doesn't just chop and change all the time. Why should it have a barrier?

John - Well when were you last in contact with a migrating goose or a swan?

克里斯- Well I saw some fly over my house the other day.

John - Yes but did you go up and rub your nose into its beak? Probably not.

克里斯- Actually no. I have to admit that I didn't.

John - Well that underlies the main problem. How does it get from one to the other? What we think happens is that the ten of thousands of geese that are currently moving around Europe get tired, they fly down onto a lake, pond or canal and they excrete virus. They are silent carriers. They don't know they're infected and they don't feel unwell. They let their waste out into the lake. Then along comes a domesticated goose or duck, it picks up the virus, doesn't get any symptoms either, passes it on to a chicken, and then the problems start.

克里斯- And why is a chicken a problem?

John - We don't know that really. It could be because chickens are pressurised with the modern farming techniques.

克里斯- What with having lots of them in a small space. I suppose that makes transmission very effective. But then how does it get into a person?

John - Well the hapless farmer comes along to admire his wonderful flock and notices that one or two of them are ill. A few days later, they're all dead. It's called wall to wall carpeting of feathers. He then realises what's happening. He calls in the vet who examines the beak and pokes a swab up their bottom. The vet is usually the first person to get in close, catch the virus and die.

Catherine - So we hear that flu is a problem in birds and in humans. What about other animals?

John - It's mainly this bird reservoir and humans. All other animals on this planet get flu. We know horses get it, whales get it. You name it and they have it, although obviously at the moment we are more interested in the human aspect than whales.

克里斯- So why should this particular strain of bird flu be an issue? Why is it more problematic than the normal strains of flu that reach our shores?

约翰-因为这是一个全新的人。这个has emerged from this reservoir and no-one has ever seen it before. No-one on this planet has any immunity to it. We're all relying on our snot basically, as that's all we've got, and of course these new drugs and maybe some new vaccines.

克里斯- So when you say we've never seen this before you're saying that most of us, because we've come across flu in the past have a degree of underlying immunity to the virus. But because this one is so different, we have no protection. Our pre-existing exposure gives no protection.

John - Yes, we're very very vulnerable, and that's what the worry is.

Catherine - But can't they just make a vaccine for it?

John - You can stock up on antiviral drugs. The class of drugs that blocks the mushroom on the virus is a very powerful class of drugs, and I think we will be relying on those. But as for the vaccine, which will also be very important indeed, one has to make a choice. I think the choice to make is to go for the virus we've got at the moment and assume that it's not going to mutate too much. We can then make some vaccines and all relax in our beds.

克里斯- Because there's some evidence that this particular strain has been in circulation for a little while before and there is a backdated or stored version of that that has been shown to be protective if it's turned into a vaccine.

John - Yes, and the most recent experiments in volunteers shows that you can get some protective immunity. You might need a lot of inactivated virus to do it, but in practice you can get something. So I think there's every reason now to press the button, make some more of this vaccine and relax a little bit.