A new European Union ban on imports of captive live birds went into effect Friday to help curb the spread of the deadly bird flu virus. The ban may also have the unintended effect of increasing the illegal trade in exotic birds.

The temporary EU ban reflects fears that bird flu could spread in the 25-member block via pet birds. Recently, for example, an imported parrot died of the deadly H5N1 strain while in quarantine in Britain.

Experts say Europe represents by far the largest market for legal exports of exotic birds from around the world. As with other species, that trade is regulated by the Convention on International Trade in Endangered Species of Wild Fauna and Flora, more commonly known as CITES. The Geneva-based organization says trade in some 1,700 bird species that fall under that convention is generally well regulated under a permit system.

CITES supports the new EU ban, but the group believes it should be lifted as soon as health risks associated with bird imports have faded. Already, says CITES senior scientist David Morgan, several African countries that export birds legally have expressed concerns about the ban.

"A lot of people from developing countries will suffer from it, because they make their living from it," he explained. "We've already had representatives from developing countries expressing concern about the implications of this. Of course, to some extent, it's out of their hands. But they're worried what the future will hold."

In fact, some experts say, the EU ban may paradoxically lead to an increase in the illegal trade in wild birds, including those carrying bird flu. Nobody knows just how big this trade is. But Damien Joly, a wildlife epidemiologist at the Wildlife Conservation Society in New York, said the illegal trade in many wild species can be lucrative.

"The trade in captive wildlife in general is huge," he said. "In some parts of the world it rivals the drug trade in terms of the volume and the dollars and the money associated with it. I don't know specifically bird trade vs. turtle trade, for example. But the global trade in wildlife is huge."

Besides banning bird imports, Mr. Damien says the EU and other countries should pressure Asian governments to crack down on wildlife markets where species are sold openly. Besides being illegal, he says, these markets also have a huge potential of spreading infection, possibly including the bird flu virus.