New WHO Director-General Margaret Chan poses for photographers on her first day in office at the World Health Organization's (WHO) headquarters in Geneva Jan. 4, 2007.

Dr. Margaret Chan on Thursday took office as director-general of the World Health Organization (WHO) following her election in November.

Chan, 59, is from the Hong Kong Special Administrative Region of China. She is the first Chinese national to head a U.N. specialized agency.

Speaking to WHO staff on Thursday, Chan pledged that both her tenure and the effectiveness of the WHO would be judged by the impact they have on two specific populations.

"I want my leadership to be judged by the impact of our work on the health of two populations: women and the people of Africa," Chan said. "WHO has a long history of commitment to those in greatest need, including the most vulnerable groups."

Chan set out six areas on which she intends to focus the work of WHO: development for health, health security, building the capacity of health systems, developing better information and knowledge, enhancing partnerships and improving the performance of the WHO.

She said that the priorities she has emphasized since her election will not mean a major restructuring of the organization. "I will stick with my promise. Reform, yes. Upheaval, no," she told WHO staff.

Chan said one of the key challenges now facing WHO is to "manage all this vigorous interest in health in ways that ensure lasting improvements and do not overburden recipient countries."

"As the acknowledged leader in public health, we need to ensure that the growing number of health initiatives meets comprehensive health needs, in a coordinated way, in line with the priorities of countries and their populations," she said.

The new WHO chief said a period of transition would last until the end of 2007 and that she would make a key statement of her vision for the agency at the World Health Assembly in May.

Chan was appointed by the World Health Assembly in November 2006, following the unexpected death of her South Korean predecessor, Dr.Lee Jong-Wook. Her term of office will expire on June 30, 2012.