GENEVA - Margaret Chan, director-general of UN World Health Organization, will step down in July after 10 years of service, a period which has seen the public health sector achieve remarkable goals while tackling tough challenges.

At the opening of the 70th session of the World Health Assembly on Monday, Chan said: "The world is better prepared but not nearly well enough."

Chan, who launched a report on her time at the helm of the WHO, lauded the organization's fight against health scourges such as HIV, tuberculosis and malaria, and commended the way it has used its vast technical expertise to adapt to complex and protracted public health issues.