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Saturday, October 22, 2005

Bird Flu in Wild Birds

I've been working overtime trying to keep up with the latest news about H5N1 bird flu in Asia and Europe. The latest updated statement from National Audubon is here.

More and more evidence is coming in of wild birds being found infected with H5N1, increasing the possibility that wild birds may be spreading it from Central Asia to Europe. However, since domestic ducks can also transmit the virus without showing signs of infection (see abstract of latest study here), legal and illegal movement of domestic ducks is another potential source of virus transmission that we may not have a good handle on.

Latest reports of wild birds with H5N1 include Mallard, Garganey, Great-creasted Grebe, Green Sandpiper, and Coot in Russia, Bar-headed Goose and Whooper Swan at Erhal Lake in Mongolia, and a boat intercepted off the coast of Taiwan held an illegal shipment of cage birds out of China that included mynahs, a black-naped orioles, and Chinese nightingales infected with H5N1. Whooper Swans have also tested positive for H5N1 in Croatia and Romania. Right now, most testing for H5N1 occurs when sick birds are found. That's a good way to help confirm H5N1 outbreaks, but does little to help understand where the virus is, the full range of species it is infecting, and the risks of transmission to other domestic and wild birds.

What we really need is a comprehensive, systematic, and long-term program to survey avian viruses in multiple species across the globe. Checking for viruses only when we find sick birds is like taking a wind speed reading during a hurricane--valuable info, but not as valuable as the ability to track, predict, and prepare for a hurricane when it is still at a distance. Right now, there is a potential hurricane of avian influenza--but we don't have a good idea of when and where it might strike. We don't know how many bird already have H5N1, where those birds are, and what other avian influenza strains are out there that it might swap genes with.

Imagine hurricane predictions without doppler radar. That's just about where we are at with avian influenza tracking right now. Researchers in Alaska are testing waterfowl for the virus, including Steller's Eider, Emperor Goose, and Northern Pintail. Canada has started a system to survey mallard flocks for avian influenza viruses--but what about other waterfowl and shorebirds species? With more reports of Passerines (song birds) testing positive for H5N1, maybe we should be testing more widely? A United States Interagency Working Group is working on a plan to test for H5N1 across the United States in response the the current threat--but what is needed is a longer-term plan to not only test for H5N1, but to track all avian influenza strains. We don't just need a way to track this influenza storm, but future storms as well.

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