Bird flu expert Dr. Margaret Chan won the nomination Wednesday to become the world's top health official, a position that would make her the first Chinese national to hold a top U.N. post, delegates said.

The victory for China, which had nominated and backed Chan, indicated the massive nation's interest in playing a bigger role in global affairs.

The executive board of the World Health Organization chose Chan to be WHO's next director-general over four other candidates in a tight race to fill the post vacated by the death last May of Lee Jong-wook. But in the final round of voting she easily defeated Mexico's health minister, Julio Frenk, by a vote of 24-10.

The nomination of Chan has to be approved by a two-thirds majority Thursday at a special session of the agency's governing World Health Assembly, comprised of all 193 member countries. In the past the votes have followed the recommendation of the executive board.

Chan, who was Hong Kong's health director in fighting the SARS outbreak in 2003 and took over as WHO's influenza pandemic chief in 2005, also has experience in containing a bird flu outbreak.

As assistant director-general, she has led WHO's efforts to fight the spread of communicable diseases and most immediately to prepare for a possible pandemic should the bird flu virus mutate into a strain easily transmitted among humans.

Appointed Hong Kong's director of public health in 1994 while the city was still under British rule, she faced her biggest test when the city was hit by bird flu in 1997 and SARS — or severe acute respiratory syndrome — in 2003, killing several hundred people.

The two diseases dealt a heavy blow to Hong Kong's economy, and Chan ordered swift action to contain their spread, averting further loss of life and damage to the city's image.

The city reported the world's first known human outbreak of the H5N1 bird flu virus in 1997, when 18 people were infected and 6 died. Chan is credited with heading off a major human health crisis by ordering the slaughter of Hong Kong's entire poultry population — about 1.5 million birds.

Chan, who earned her medical degree from the University of Western Ontario in Canada, joined the Hong Kong Department of Health in 1978 and has spent most of her career in administration.

The other candidates in the final shortlist were Dr. Shigeru Omi, a Japanese national who heads WHO's operations in Asia; Spanish Health Minister Elena Salgado Mendez; and Kazem Behbehani, a senior WHO official from Kuwait.