Fears that the deadly H5N1 Avian flu virus could be evolving into an even deadlier strain are emerging in Egypt. There have been reports that a flock of vaccinated birds have been diagnosed with the deadly virus, despite preventative measures.

Dr. Suhir Hallaj, director of the World Health Organization's communicable disease program, says there is particular concern for Egypt as victims have suffered respiratory problems.

The case of Nadia Hafez, who died in Egypt's Fayoum region last month, is of special concern. Hafez experienced multi-organ failure and failed to respond to anti-viral drugs.

Despite growing concern, all the Egyptians who have died had direct contact with sick birds. However, the recent discovery that birds vaccinated have tested positive for the H5 N1 strain has increased fears that the virus could cross species barriers, which could cause a worldwide pandemic and claim lives on an unprecedented scale.

Egypt is a high risk area for bird flu as it is directly on the path for migratory birds from Europe and Africa.