ROME -- Most of the scattered bird flu outbreaks so far this year probably can be traced to illegal or improper trade in poultry, scientists say. That includes recent outbreaks in Nigeria and Egypt as well as the large outbreak on a turkey farm in England.
Last winter, wild migrating birds were deemed the primary culprit in the bird flu infestations that hopscotched across Europe and Africa.
Dead swans and ducks were found in many countries, including Austria, France, and Italy.
"Many of us at the outset underestimated the role of trade," said Samuel Jutzi, director of Animal Production and Health at the United Nations Food and Agriculture Organization in Rome.
"The virus is behaving rather differently than last year -- it's rather enigmatic," he said.
No outbreaks have been attributed to wild birds so far this season, and not a single infected wild bird has been detected in Europe or Africa, despite a heightened surveillance system devised following the crisis last year.
In most parts of the world, there have been far fewer outbreaks compared with a similar period in 2006.
In Europe, there was one outbreak in Hungary in January and another this month on a turkey farm in Suffolk, England.
Investigators from the Food and Agriculture Organization and the British government suspect that trade may have set off those outbreaks. The poultry farm that was the site of the outbreak in Suffolk was owned by a company, Bernard Matthews, that also raises birds in Hungary, said a spokeswoman for the British Department for Environment, Food and Rural Affairs, which is investigating the outbreak.
Partially processed meat was routinely shipped from the company's Hungarian farm to the one in Suffolk for final processing. Although the avian influenza virus is killed by cooking, it survives well in raw meat and such shipments may have transported it to England. It could have been carried from the processing plant into the animal pens on workers' shoes or farm equipment.
Indonesia, Egypt, and Nigeria have emerged this season as persistent bird flu trouble spots, with constant cases in birds and some transmission to humans. Trade may play a role in these countries as well, officials said.