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Last Updated: Sunday, 6 November 2005, 20:44 GMT
Early bird flu warning for Dutch
Jan Van Kampen with Jane Corbin
Jan Van Kampen's (left) farm was affected by the outbreak
In February 2003, at a time when the world was focused on containing Sars, the Netherlands was battling a different infection: bird flu.

A highly pathogenic strain of avian influenza began to spread through chicken flocks in one of the country's densest poultry farming areas.

It spread very quickly through farms and caused real alarm in a country where the export of poultry and eggs brings in 284m euros a year.

As well as concerns for the economy, there were fears for human health: in 1997, in the first outbreak of H5N1 in Hong Kong bird flu had managed to infect humans who had come into contact with birds. In that outbreak 18 people had been hospitalised and six had died.

Knowing what had happened in Hong Kong, the Netherlands did undertake to protect all those who they charged with the culling of infected birds by distributing masks, eye protection, gowns and caps. But this strain had never infected humans before and the risks were thought to be low.

Taken by surprise

Despite the precautions, human cases were being anecdotally reported within a week.

PANORAMA
Bird Flu - Facing the Pandemic
Sunday 6 November 2005

The symptoms were mild, in most cases it caused conjunctivitis, but health protection units were suddenly alert to the possibility of a flu pandemic developing through mutation or a mixing of the virus with a human flu already in circulation.

Human health protection teams soon joined their veterinary counterparts on the ground but the measures they enacted were not enough to prevent one person, a 57-year-old veterinarian named Jan Bosch, from dying as a result of the disease.

Four months after the outbreak began it was brought under control. 30m chickens had been killed to curb the disease's spread. 89 humans had been infected by the virus and one person had died.

Since then scientists and policy makers have been looking at the outbreak in order to understand exactly what happened.

A key question for scientists was: why did a disease which gave most humans a mild conjunctivitis, lead to a person's death?

'What made it a human killer?'

Influenza viruses are highly unstable; as they reproduce, they can mutate.

The virus which killed Jan Bosch was H7N7 but it had mutated and become more virulent.

The first symptoms appeared just two days after the 57-year-old had visited an infected chicken farm and spent just two hours screening flocks.

He got a headache and a fever. The family doctor took swabs in case it was H7N7 but for reasons which are unclear the results he got back were negative.

Six days later his condition had deteriorated and he was taken to hospital. Chest X-rays showed pneumonia. He was moved to intensive care and put on a ventilator, but it wasn't possible to save his life.

He died just two weeks after first becoming ill. H7N7 was discovered at autopsy: there was a lot of the virus in his lungs.

The way in which H7N7 attacked, in this case, is similar to the way in which H5N1 - the current strain of flu affecting chickens, ducks and wild birds - has attacked humans in the cases where it has jumped species: it is the lungs which the virus attacks.

No one surrounding the vet caught the virulent form of H7N7 from him. However no one can say categorically whether it could have transmitted or not.

Indeed in some families in the Netherlands the milder form of H7N7 was transmitted from one person to another, so that people who had not had direct contact with chickens nonetheless caught the illness.

This transmission was limited but, if it had been able to spread further and faster, we would have been looking at a much more dangerous situation and potentially a new pandemic starting on European soil.

Where did it come from?

A team in the Netherlands had already been monitoring low-pathogenic, avian influenza in wild birds.

Avian influenza is always present especially in waterfowl like wild ducks but it is not usually something which kills.

However, when a low-pathogenic virus finds its way into domestic chickens, it spreads fast and furiously and can mutate into something much more virulent. This appears to be what happened in the Netherlands.

A low pathogenic avian influenza which had been circulating in wild birds bears a close genetic resemblance to the highly pathogenic H7N7 which later emerged.

Furthermore, the outbreak began on a free-range farm where chickens were more likely to come into contact with germs shed by wild birds.

The virus was most probably carried by migrating mallard ducks. They would have had no symptoms themselves but when the flu was picked up by domestic chickens it mutated into a deadly form.

The same process would have occurred with H5N1, the strain currently affecting poultry in South East Asia though in this case the transmission between wild and domestic birds has gone one step further.

Probably the low-pathogenic flu was transmitted from wild to domestic birds and became highly pathogenic back some years ago. This year it was discovered that the highly pathogenic form, which developed in chicken flocks, has been passed back to wild birds.

Why the Dutch are nervous

This is something which has never been documented before and it makes farmers and scientists in the Netherlands particularly nervous.

In the Netherlands poultry farming is particularly dense. There are about 90m chickens and a human population of just 16m.

An outbreak of this virus, which would not even have to mutate to start killing poultry, would be very hard to contain and likely result in another massive cull.

Jan Van Kampen sorting eggs
Jan Van Kampen has moved his chickens inside as a precaution
In October 2005 Panorama visited one of the farms which was affected by the 2003 outbreak. The farmer there, Jan Van Kampen, was already keeping his flocks indoors as a precautionary measure to reduce the risk of them catching H5N1.

Normally his flock is free range and would be out in the fields. He told Panorama that after the 2003 outbreak he did not have any income for a year, because he was not allowed to keep chickens in the same barns until they could be sure they were free of the virus.

The outbreak in the Netherlands shows the significant advantages which a Western European county has when it comes to tackling outbreaks of avian influenza.

The method of killing birds using CO2 gas pumped into the barns (which has also now been tested in the UK), contrasts with some of the slower culling methods used in South East Asia and ultimately the cull was very effective.

However, despite the distribution of goggles and masks and an advanced public health system, people still caught the flu from the birds and one person died.

The fact that the symptoms which developed were mostly mild forms of conjunctivitis perhaps meant that poultry workers were not that worried about the virus and were not careful enough.

As one public health official put it, the workers did not understand 'the big picture' that the virus could mutate in humans to become more virulent or mix with a human flu to form a pandemic strain.

If called upon to tackle an outbreak of bird flu in chickens in the UK, government ministers and officials will have the threat it poses to human health at the front of their minds.

FURTHER READING:

Transmission of H7N7 avian influenza A virus to human beings during a large outbreak in commercial poultry farms in the Netherlands - M. Koopmans et al, Lancet, Vol 363, February 2004

Avian Influenza A virus (H7N7) associated with human conjunctivitis and a fatal case of acute respiratory distress syndrome. - R. Fouchier et al, PNAS, Vol.101 no.5, February 2004

The Monster at our Door (M. Davis)

Panorama's "Bird Flu - Facing the pandemic" was broadcast on Sunday 6 November 2005 on BBC One and online at bbc.co.uk/panorama

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