Michael Richardson: Flyways of destruction

Senior epidemic and disaster management co-ordinators from New Zealand, Australia and the other 19 Apec member economies are meeting in Brisbane today to tighten the region's preparedness for managing an avian flu pandemic.

They will have to consider how real the risk is now that the deadly form of avian flu has reached Europe from Asia in barely three months in a series of long-distance jumps.

Until July, outbreaks of the H5N1 virus were restricted to East Asia. Since then, the infection has been confirmed among birds - chiefly farm poultry - in parts of western China, Asian Russia east of the Ural Mountains, Kazakhstan in Central Asia and now Turkey, Romania, European Russia, Croatia and Greece.

There is increasing evidence that bird flu is being spread by wild waterbirds - mainly in the Anatidae family of ducks, geese and swans - as they migrate from their spring-summer breeding grounds in Russia and other parts of the Northern Hemisphere.

Migratory birds travel in huge numbers along overlapping routes called flyways. These aerial highways stretch from the far north of the Eurasian landmass to Africa, India, New Zealand and Australia.

Several of these flyways straddle Europe. The one that is bringing waterbirds into the Balkans and the Danube delta, Europe's largest wetlands near the Black Sea, is known to ornithologists as the Black Sea-Mediterranean flyway.

Most of the birds using this route are heading for the Middle East, North Africa and East Africa.

If this epic movement of wild birds from north to south and back again every year has become a conveyor belt for avian flu, it has disturbing implications.

The United Nations' Food and Agriculture Organisation (FAO) has warned that the northwards migration of birds in spring next year may spread the H5N1 virus further into Europe because birds coming from southern zones will have mixed with migrants from the north.

The avian flu virus is shed in birds' faeces and saliva. It is passed among ducks, geese and swans that share common water and resting areas with farm poultry, which often happens in Asia, Europe and Africa. Worse still, in poor areas of Africa and Eastern Europe people live in close proximity with their poultry and other farm animals, as they do in Asia.

This will provide a dangerous crucible for mixing bird and human viruses, increasing the risk that the avian virus could gain the ability to spread easily from person to person and cause a pandemic.

The same mixing may happen in Asia as migratory ducks, geese and swans fly from northeast Asia to Southeast Asia, stopping frequently along the way in wetlands for food and rest.

But these birds have not been recorded going further south than Indonesia.

The several million migratory birds that fly in and out of New Zealand and Australia each year along the East Asian-Australasian flyway are shorebirds.

Thirty-six species are involved, mainly snipe, godwits, curlews, redshanks, sandpipers, knots, stints, plovers and pratincoles. Some travel as much as 26,000km on their return journeys between New Zealand and Siberia.

Scientists have reported finding avian influenza viruses among migratory shorebirds, including some of the species that fly to and from Australasia. But they say that the incidence is much lower in waders than in migratory ducks, geese and swans.

There has been no reported finding of a highly pathogenic flu virus like H5N1 from shorebirds anywhere in the world.

Although the deadly H5N1 virus has devastated poultry flocks and killed 60 people in Southeast Asia, it was never recorded in wild birds before the recent outbreaks of bird flu in Asia, Russia and countries around the Black Sea.

In the past, highly pathogenic viruses have been found only very rarely in migratory birds.

They were usually found dead within flight range of an outbreak of virulent bird flu among poultry, leading scientists to believe that wild waterfowl were not agents for the onward transmission of the lethal viruses.

But something has changed and it is an ominous development.

The World Health Organisation says that some migratory birds now appear to be directly spreading the H5N1 virus in its highly pathogenic form over long distances and that further spread can be expected.

It also says there is considerable circumstantial evidence to suggest that when they mix with domestic poultry, wild waterfowl can introduce to farm flocks low pathogenic viruses which then mutate to the highly pathogenic form, including the H5N1.

Still, the FAO points out that the pattern of H5N1 outbreaks in East Asia does not coincide with the migratory routes used by wild birds for all countries.

For example, many duck species that carry avian flu viruses spend the Northern Hemisphere winter in large numbers in Taiwan, the Philippines and South Asia, which have not reported confirmed cases of lethal bird flu.

Moreover, the H5N1 outbreaks in Indonesia and Malaysia happened when migratory birds would not normally have been in those countries.

The risk that deadly avian flu will be brought to New Zealand by migratory birds seems low.

The biggest risk is the one that faces the world as a whole: if the H5N1 virus changes into a strain that can spread easily from person to person and has a high infection and death rate, it will be difficult, if not not impossible, to stop.

* Michael Richardson, a former Asia editor of the International Herald Tribune, is a visiting senior research fellow at the Institute of Southeast Asian Studies in Singapore.