While bird flu has become a huge problem in poultry on farms in a few African countries, including Egypt, Nigeria and Sudan, specialists increasingly suspect that it was introduced in those countries through imported infected poultry and poultry products. Mr. Hagemeijer said the strength of the virus among wild birds possibly weakened as the southward migration season progressed, a trait he said was common in less dangerous bird flu viruses. That probably limited its spread in Africa, he said. (NYT)