Margaret Chan Guardian's Series: Top 100 women: activists and campaigners

Director of the World Health Organisation, battling international viruses, and championing improvements in all of our most pressing diseases

• Homa Khaleeli
• The Guardian

Margaret Chan, director of the World Health Organisation. Photograph: Fabrice Coffrini/AFP/Getty Images

Margaret Chan, 64, has been on the frontline of the global fight against swine flu, Sars and bird flu – and is now said to be the most powerful international public health official in history.

Originally a teacher, she trained as a doctor in Canada before returning to Hong Kong and heading the health department – just in time to have to deal with an outbreak of bird flu. After initially trying to reassure people chicken was safe to eat, she ordered a cull of all 1.5 million ducks and chicken in the country – and her decision was seen as crucial in stopping the virus. She was also at the helm when Sars hit, and while she was criticised for what was seen as a slow response, the then director general of the WHO was so impressed that he headhunted her. saying, "You are the only person who has managed crises. I have many armchair experts. I need generals."

As well as battling international viruses, she is also trying to champion improvements in maternal care, HIV and Aids care, malaria, and all of our most pressing diseases. When she was made director in 2006 she was clear about her priorities: "What matters most to me is people. And two specific groups of people in particular. I want us to be judged by the impact we have on the health of the people of Africa, and the health of women."

However it was not long before she has to turn her attention again to global viruses. In June 2009 she became the first WHO chief in 41 years to announce a worldwide pandemic when swine flu swept across the globe. This time around critics complained the public health expert had overreacted. The Council of Europe accused the WHO of having "gambled away" public confidence by overstating the dangers of the flu pandemic, in a draft report. But Chan is unrepentent, firmly stating,"That was the right call," - and in the UK at least the response to the pandemic was proportionate and effective, according to an independent review.