The H5N1 strain of bird flu has been circulating in Asia since late 2003 and has spread to parts of Europe and Africa. Experts believe it could mutate into a form that is easily spread among humans, sparking the next flu pandemic.

The World Health Organization has recorded 154 human deaths worldwide from H5N1, and most of those victims came into direct contact with infected birds.

Leavitt said the United States has formally accepted the WHO's revised International Health Regulations on preventing and responding to infectious disease threats. While the regulations are to take effect June 2007, many countries - including the US - have adopted them effective immediately.

The revised list adds and prioritizes smallpox, polio, SARS and new strains of human influenza, while the original list applied to cholera, yellow fever and plague.

Last week, Leavitt went to a village in the central province of Hunan to visit a 9-year-old girl who recovered after being infected with H5N1, and talked to local leaders and doctors who diagnosed and treated her - all rare access for a foreigner.

One of the doctors had a computer that allowed him to update a national database on communicable disease, Leavitt said. That allowed them to see where cases of TB were occurring and track on a daily basis the number of AIDS cases being diagnosed, he said.

"What each of those tell me is that they are placing a great deal of importance on infectious disease control and prevention," Leavitt said.

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