By Irwin Arieff UNITED NATIONS, Oct 23 (Reuters) - The threat of a bird flu pandemic is transforming poultry industry practices around the world, but health officials must remain on high alert for five to 10 more years, a top U.N. official said on Monday. The bird flu virus can reside in flocks for long periods of time, showing no symptoms, before spreading to new areas via trade or migration, said Dr. David Nabarro, who heads the U.N. drive to contain the disease in birds and prepare for its possible transformation into a fast-spreading human disease. It will also take more than a decade for those raising poultry to make needed changes in the way they operate to keep the disease under control, Nabarro added. For now, the disease continues to menace both birds and humans. A total of 256 people have been infected and 151 have died from the disease in nine countries since 2003, according to the Geneva-based World Health Organization. In Indonesia alone, a densely populated developing country of 220 million people with a heavy concentration of poultry, the virus has killed 55 people, causing U.N. health officials "very great concern," Nabarro said. While Indonesia has taken significant steps to change the way it raises poultry to lower the risk of a pandemic, "still there is such a lot to be done" to ensure both animal and human safety, he said. A little over a year ago, new to the job, Nabarro told reporters at U.N. headquarters he feared bird flu could end up killing as many as 150 million people if the world failed to adequately prepare for an expected mutation of the virus, enabling it to easily spread among people. Nabarro did not think the crisis had been overblown. "When we are saying there is a risk of something bad happening," he said, "if that bad thing doesn't happen in the immediate future after we have said that there is a risk, people are prone to say, 'Well perhaps you've exaggerated.'" "I can understand that. However, there will be an influenza pandemic one day. I don't know -- you don't know -- when it is going to be. When it does come along, it will have really major economic and social consequences," he said. The H5N1 bird flu virus is "extremely vicious" and now affecting poultry around the world except for the Western Hemisphere, he said. It kills birds "incredibly rapidly," can infect humans and could mutate to a form that could cause a human pandemic, he said. "There are probables in there. There are certainties in there. But the one absolute requirement on the basis of this is, we have to get prepared for the pandemic."
