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Last Updated: Sunday, 13 November 2005, 19:24 GMT
Prof Albert Osterhaus

Professor Albert Osterhaus
Professor Albert Osterhaus is a virologist based at the Erasmus Medical centre in Rotterdam. He is also director of the National Influenza Centre in the Netherlands. The following is a transcript of an interview with Panorama's Jane Corbin, recorded on the 4 October 2005 in Rotterdam.

Jane Corbin: Is there a real fear of migratory birds carrying H5N1 which might come from Russia or Kazakhstan?

Albert Osterhaus: In the Netherlands we are very concerned. In 2003, we saw a massive outbreak of avian flu in our domestic poultry flocks, and we had to slaughter more than 30 million chickens, you know, so there was huge cost, huge animal welfare problems, so you can imagine that we are very concerned that it would happen again.

If infected birds can make it all the way to Western Europe, either directly or through contact with other birds so that they would pass on the virus to other birds, then this highly pathogenic virus could get directly into the European area, where we have a lot of free range birds.

We saw in 2003 that another avian flu virus that was still a low pathogenic virus, crossed the species barrier, and went from these wild migratory birds, directly into our domestic flocks in the Netherlands. It was migratory mallards most probably that brought it to the Netherlands, and this was a low pathogenic virus meaning that still when it got to the birds, the birds didn't get sick.

But now, if we have one of these deadly highly pathogenic viruses already in the wild birds, and they migrate all the way to Europe, for instance to the Netherlands, this virus wouldn't have to mutate anymore, but could directly cause fowl plague in the Netherlands.

Jane Corbin: So the birds in the domestic poultry area could get it, and from there we know that there can be transmission from domestic birds into humans.

Albert Osterhaus: We know that it can be transmitted from domestic birds to humans, we have seen that happening more than 120 times now in South East Asia. More than 65 people have died, so this is a dangerous virus for humans. But on the other hand, I think when we look at the problem in South East Asia, it is absolutely not under control, whereas if this were to happen again, for instance in the Netherlands, we would know how to handle it.

We would treat the cullers and the farmers preventively to stop the virus from spreading into the human population. So the risk of human infection in Europe is much less than in South East Asia, where you have so many more cases, and the virus is all over the place, and we see it spreading to humans every now and then. The risk in Europe, primarily, is, is the risk of a fowl plague outbreak.

Jane Corbin: And is there a danger that a similar thing could happen in Britain?

Albert Osterhaus: Well, that really depends on the migratory pathways of the birds, and we know that, for instance, there's a lot of geese in the Netherlands, a lot of mallards, and there's actually millions of birds that migrate every year, and that includes the UK as well. So we know there's a lot of Mallards and other species that also migrate to the UK, and there is free-range poultry there as well.

Jane Corbin: Now, our officials have said there's a very low risk of that happening, do you think that's correct?

Albert Osterhaus: I think at this moment, we just haven't got the data. We know there is a risk, we know that birds can carry the virus, either directly or indirectly. There are people who say that all the birds that get infected will actually die but we don't have that data, we don't know that. So I think at this moment, there is a real chance that this virus could be trafficked by the birds all the way to Europe. There is a real risk, but nobody can estimate the risk at this moment, because we haven't done the experiments. You could have a situation where an older bird, has been infected previously with a low pathogenic H5N1 virus, which more or less that works as a vaccine. The bird builds up an immune response against that virus, and then when it gets super infected with this very lethal virus, it will be immune to the virus. And that's another way in which you can imagine that these birds can carry the virus directly without dying.

Jane Corbin: I want to take you back to February 2003, what happened there?

Albert Osterhaus: An influenza virus spilled from wild birds into our free-range chickens and from there into the bio-industry. This made it necessary for us to cull all together more than 30 million chickens in the Netherlands. So that was quite an operation, for which we were not really prepared. We had to involve many cullers, and farmers.

Initially we were quite relaxed about the possibility that this virus would be very dangerous for humans. We realised that there was a possibility that this virus would also be dangerous for humans, so we took a lot of precautionary measures during this culling exercise.

We gowned up all the cullers, gave them goggles and caps and mouth masks and we also gave them Tamiflu, an antiviral, so all the people that would be exposed to the animals, the dead animals, or the live animals and their manure, were actually treated preventively with this antiviral.

In addition to that, we also vaccinated them against the normal winter flu, winter influenza that was spreading at the time in the same area. So all these measures, of course, they were quite expensive measures but the compliance was not too high. At the end of the day we saw that about 90 people, actually 89 people developed systems. Most of them developed conjunctivitis, an inflammation around the eye, and some of them also developed an influenza-like illness, which could be rather, rather severe. And also what we saw is that some of the family members of the poultry workers, of the cullers also became infected. So we saw person to person transmission in the Netherlands as well.

Jane Corbin: So this made it clear that avian flu could transmit into humans and be passed on, even if only in a limited way. It was capable of being passed on?

Albert Osterhaus: We saw that in a very limited way as you said, that this virus was also spreading from person to person, but not efficiently enough to really keep spreading amongst the population, the Dutch population, so it stopped at the secondary cases. If it had spread further, then we would have been of course in a much more dangerous situation, but fortunately it was very limited spread there.

Jane Corbin: What was the reaction of the scientific community to this? Obviously it was a terrible shock for Holland for the industry, but also for scientists knowing that this was possible.

Albert Osterhaus: Well, we already knew of course from what happened in '97, in Hong Kong where we had 18 people hospitalised, 6 of whom died during an outbreak of H5N1 avian influenza. That was the first time that we realised that an avian influenza virus could transmit directly to humans. Before, it was always thought that that was not possible, that we thought, that if indeed an avian virus would, would come to humans, it would always go through, though a pig, first to a pig where the virus would exchange genetic material and from there could pass on to humans. But now we had seen that the virus could directly transmit from birds to humans. That was new since '97. Ever since, we have seen some individual cases of transmission from birds to humans, but what happened in the Netherlands in 2003, was quite unexpected, that during this culling exercise, so many people became infected. All together 89 people became infected, and later studies that have been carried out here in the Netherlands, have shown that probably more people were infected even, because in more people antibodies were found against the virus.

The real risk we were running in 2003 was that two viruses in the same area, the avian virus and the human influenza virus would mix and create a completely new virus. Fortunately that didn't happen, we did a lot of screening work at that time, and we saw a lot of people with influenza, mostly the avian influenza, but in the same area, some people also suffered from normal human influenza virus, but we didn't see any mixed infections at that time.

Jane Corbin: There was a death in this outbreak also. Tell me about that. Did you know the individual, what happened to him and what does it show?

Albert Osterhaus: This one individual was a veterinarian, and he went to a farm where, that was suspect of a starting outbreak. He took samples from, from a number of animals and sent these samples in, so he was only at this farm for a very short period of time. He developed a very severe headache, and there were samples taken from him after some time, and they were negative for the bird flu. So, they didn't suspect him of being infected with the avian virus.

And then his condition deteriorated. He developed a respiratory disease as well, and subsequently he was hospitalised. When he was in hospital, x-rays were taken of his chest, they showed that he had a pneumonia that deteriorated. After a couple of days, he needed to be put on a mechanical ventilator, and then his situation deteriorated progressively and finally he died whilst he was still on the respirator. This happened in a period of less than two weeks from first symptoms.

When we then got autopsy material from his lungs, we were able to show that there was a lot of virus in his lungs, and this was the virus that had been seen in the chickens as well, although it had accumulated a number of mutations, which we transformed the virus from a relatively low pathogenic virus for humans into a very pathogenic virus for mammals in general.

Jane Corbin: This showed that this bird flu virus could change, could be caught by a human being and change in the process?

Albert Osterhaus: We're not a 100% sure whether the virus that he died from mutated in the patient or had already mutated in the birds, but we suspect that it indeed mutated in the patient and so, there are two important issues there. In terms of pathogenicity, a virus can mutate, can accumulate mutations by which is becomes more severe to humans, causes a more severe disease. The other issue is, is the virus capable of transmitting between, from human to human? That's an independent thing, we don't know which mutations actually make it possible for the virus to spread amongst humans efficiently. Because that's really what you need for a pandemic virus. On the one hand it should cause disease obviously, but on the other it should also easily transmit from human to human to sustain itself in the human population.

When we look at what's happening now in South East Asia, on the one hand what could happen is that the virus from the birds could adapt to transmission between humans, that's a possibility. The other possibility is that you get these mixed infections where you get an exchange of genetic material between a human and an avian virus, resulting in a completely new virus, that could easily transmit from human to human. So there's two possibilities that could happen.

Jane Corbin: So how concerned are you that a pandemic could be the outcome, given where we are today?

Albert Osterhaus: It's very hard to say. I think what we have seen so far is more than 120 people who have developed disease, more than 65 of them have died and we don't' quite understand why the number of people becoming infected and developing the disease is relatively small, because we're talking about an enormous area where the disease in the poultry is not under control. It's an area where about 30% of the world population lives. However if the virus manages indeed to, to mutate itself in such a way that it can transmit from human to human, then we have a completely different situation, we might be at the start of the pandemic.

We have seen a similar thing already happening in other mammalian species now. We have seen, for instance in tigers, but also now in laboratory cats, that indeed this virus doesn't only cause severe disease, pulmonary disease, but also transmits from cat to cat. If that were to happen in humans, then we would indeed have a situation that might result in a pandemic. And we don't' actually know why it doesn't happen, and it's very difficult to predict whether indeed this virus is capable of doing that.

On the other hand you could say, if you were to draft a scenario for a pandemic virus to emerge, this is the early stages of a thing like that happening.

Jane Corbin: Isn't there a danger of scaremongering because we don't know if this virus can move easily between humans. So far, we've seen it in a number of places, but are we suggesting too much this fear of a pandemic of flu?

Albert Osterhaus: I don't think so. I think we've seen 3 pandemics in the last century, and it's just a matter of time until we have another pandemic, and nobody can tell us today whether this particular virus will be at the basis of the next pandemic. We just don't' know. But we also know that these viruses, these influenza viruses, they have the intrinsic property to mutate easily, and we don't know exactly at this moment what kind of mutations are needed to make this deadly virus, to make it possible for that virus to spread from human to human. But that could be just a few mutations or very little change in the virus.

We have seen some indication that the virus can indeed spread from human to human limitedly. The virus that can do that may have changed in such a way that it can do it again. So the more cases you see, the more risk you run that indeed a virus will emerge that has accumulated the necessary mutations to indeed spread efficiently from human to human. So the more cases you see, the greater the risk is going to be.

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