U.S. Bird Flu Detection Plan Is Wild Goose Chase, Study Says

Adrianne Appel
for National Geographic News

December 5, 2006

Officials are looking in the wrong place to stop the spread of bird flu to the U.S., a new study suggests.

The report predicts that bird flu will likely spread to the Americas through infected poultry. This poultry may then infect local wild birds, which could carry the disease from Latin America or Canada to the United States.

The U.S. is currently testing thousands of wild birds in Alaska, because authorities believe the flu is likely to be carried from Asia to the U.S. by migrating waterfowl.

(Read "Alaskan Ducks Tested for Bird Flu" [September 13, 2005].)

The new report, from the New York-based Consortium for Conservation Medicine, studied migration patterns and the bird trade. The study suggests that birds migrating from Siberia to Alaska are unlikely to carry the virus and that few of those birds ultimately fly farther south.

"We share very few migratory birds with Europe and Siberia. There are ducks and geese that winter in Siberia and molt in Alaska, but they don't come down here," said research scientist A. Marm Kilpatrick, co-author of the study.

The U.S. has also been trying to keep the disease at bay by testing and quarantining all poultry imported from infected regions of Europe, Asia, and Africa.

But there is very little poultry trade between Asia and Europe and the U.S., Kilpatrick said, so the risk of the U.S. getting infected that way is very low.

Furthermore, few birds migrate between Europe and the Americas, Kilpatrick added.

A far greater risk is that many countries in Latin America import poultry from infected regions of Europe and do not have strict testing and quarantine systems in place, Kilpatrick said. In addition, more than four million birds migrate annually between the U.S. and Latin America.

"If your neighbor gets the virus and birds migrate, you're at risk,'' he said.

His team's research appears in today's issue of the Proceedings of the National Academy of Sciences.

Triple Threat

The H5N1 avian virus originated in Hong Kong and spread rapidly through much of Asia before continuing to Africa and Europe.

It is fatal to birds and can be transmitted to humans through close contact with birds, for example, on poultry farms.

So far the disease has killed 151 people, but the virus in its current form cannot be transferred from human to human. (Read "Bird Flu: Frequently Asked Questions.")

In his team's current research, Kilpatrick found that the virus spread through Southeast Asia primarily through the poultry trade, but migrating birds were mainly to blame for carrying the disease from Asia to Europe.

"The question now is, How will it get to the U.S.,?" Kilpatrick said.

(See National Geographic magazine's "Tracking the Next Killer Flu.")

Ken Rosenberg of Cornell University's Laboratory of Ornithology was not involved in the study, but he agrees that testing birds in Alaska may not protect the U.S. from the virus.

"To my knowledge, all the testing has been negative. They haven't found it coming in through birds that way,'' Rosenberg said.

Rosenberg thinks it's possible that the virus will come to the U.S. from Latin America, not through migrating birds but through the legal or illegal pet-bird trade.

Mulit-Nation Plan Is Key

Kilpatrick's team found that the virus has spread easily so far due to both the global trade in birds and the migration of wild birds, chiefly geese, swans, and ducks.

The team examined the spread of the virus into 52 countries. In each instance the researchers determined whether transmission occurred through the legal poultry trade, the wild-bird trade, migrating birds, or some combination of these.

The scientists also estimated the number of birds that enter or leave a country, how many of them were likely infected, and how long the birds remained contagious.

The team then ran genetic tests on the viruses found in infected birds, which helped reveal how the virus spread from region to region.

Turkey, for example, has a thriving poultry trade with Thailand as well as a heavy influx of migrating birds from Russia. Scientists weren't sure which pathway brought the virus to the country.

"But then we took a look at the [genetic] isolates, and they were much more related to Russia," Kirkpatrick said.

This led his team to conclude that the likely source of bird flu in Turkey was Russian migrating birds.

The case of Turkey may offer a lesson the U.S., Kilpatrick suggested.

An effective way to keep the U.S. free from bird flu would be to work with Latin American countries on a regional system of testing and quarantining imported poultry, he said.

"If we want to be as safe as possible, we would want all our neighbors to have the same safeguards we do," Kilpatrick said.

His team has not heard from U.S. policymakers about the suggestions put forward in the new study. But Kilpatrick said he hopes decision-makers will refer to the research when considering future bird-flu prevention plans.

"If you're going to make policy decisions, it's best to look at data,'' he said.

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