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Monday, May 15, 2006

Birdchaser in Science

On Friday, Science Magazine published the following letter to the editor. Some great folks co-authored the letter. Nice to be associated with such fine company.

Migratory Birds and Avian Flu
In his article "Evidence points to migratory birds in H5N1 spread" (3 Mar., p. 1225), D. Normile reports that "increasingly, scientists are attributing this remarkably fast spread [of H5N1] to migratory birds, but dissenters remain."

All agreed that wild birds have a role, but attributing the spread of HPAI H5N1 entirely to migratory birds overlooks evidence that is inconsistent with this conclusion.

One cannot ignore the apparent lack of previous outbreaks along migratory pathways. Birds have been migrating along these same routes annually since this genotype of HPAI H5N1 was first identified in Asia in 1997, yet there was no spread of disease to Eurasia or Europe in the interim years. Although fewer than 0.05% of more than 13,000 healthy waterfowl tested (1) were positive for HPAI H5N1, billions of birds have traveled to Eurasia and Europe for 8 years. It seems suspicious that none has managed to transmit this highly pathogenic virus until now. The introduction of HPAI H5N1 onto the continent of Africa, as well as the earlier outbreaks in poultry, notably in Russia and Turkey, could have been as easily accommodated by the movement of infected poultry, poultry products, or contaminated fomites as suggested for migratory bird routes. Meanwhile, Japan, with strong controls on poultry imports, has remained H5N1-free since early 2004, when infected poultry flocks were destroyed, despite the annual arrival of large migratory bird populations from areas with known H5N1 outbreaks.

Four pathways are most likely involved in the movement of HPAI H5N1: poultry shipments; the movement of contaminated equipment, materials, and waste products; migratory birds; and the wild bird trade. At most, the evidence suggests that wild birds may be responsible for short-distance, secondary movement of HPAI H5N1. Ornithologists, virologists, veterinarians, and others must work together, sharing their specialized knowledge to understand more thoroughly the movement of this virus.

Rob Fergus
National Audubon Society
545 Almshouse Road
Ivyland, PA 18974, USA

Michael Fry
Pesticides and Birds Program
American Bird Conservancy
1731 Connecticut Avenue, NW
Washington, DC 20009, USA

William B. Karesh
Field Veterinary Program
Wildlife Conservation Society
2300 Southern Boulevard
Bronx, NY 10460, USA

Peter P. Marra
Smithsonian Migratory Bird Center
National Zoological Park
3001 Connecticut Avenue, NW
Washington, DC 20008, USA

Scott Newman*
Field Veterinary Program
Wildlife Conservation Society
2300 Southern Boulevard
Bronx, NY 10460, USA

*Previously at Wildlife Trust,
460 West 34th Street, 17th Floor,
New York, NY 10001, USA.

Ellen Paul
Ornithological Council
1707 H Street, NW
Washington, DC 20006, USA


H. Chen et al., Proc. Natl. Acad. Sci. U.S.A. 103, 2845 (2006).

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