Chan also told WHO's annual meeting that she was putting in place a new "unified" programme to help deal with health emergencies.
Following the 2014 Ebola outbreak which has so far claimed over 11,000 lives, the World Health Organization (WHO) is to set up a $100m (about N20 billion) emergency contingency fund.
Margaret Chan, WHO Director-General who was speaking in Geneva said WHO had been overwhelmed by the epidemic in West Africa adding that the demands were more than 10 times greater than anything else it had experienced.
Chan also told WHO's annual meeting that she was putting in place a new "unified" programme to help deal with health emergencies, saying she did not "ever again want to see this organisation faced with a situation it is not prepared, staffed, funded, or administratively set up to manage,"
She added that the changes would be completed by the end of the year.
The Ebola outbreak which was first detected in December 2013 has claimed over 11,000 lives with the highest number of casualties coming from Liberia, and has since been declared Ebola-free by the organiation.