The World Health Organisation chief has been under severe criticism because of its slow response last year to the Ebola outbreak, which has now battered three countries in Africa and resulted in thousands of deaths.

A United Nations mission in Liberia repeatedly sent warnings to the WHO about the outbreak, but her office said it had no record of ever receiving them. Months after the virus became headline news, the WHO declared it a global medical emergency. By then, more than 1,000 people were dead and the virus had spread to Nigeria, Africa's most populous country.

The WHO's delayed response to Ebola contrasts with its speed to declare swine flu a full-blown pandemic in 2009, only to face ridicule when it turned out to be much less lethal than thought.

It appears Chan is ever ready to defer to the governments in question, as in the Ebola case.

When polio broke out in war-torn Syria in late 2013, or when Middle East respiratory syndrome spread in Saudi Arabia, the WHO accepted at face value that their governments had the problems under control.

In 2010, after a brief visit to Pyongyang, Chan said this of North Korea's national health-care service: "They have something which most other developing countries would envy."

Of course, there was no point for Chan to confront a regime like Pyongyang, as criticism would only invite retaliation and obstruction. Still it's a distance going from non-criticism to actual praise.

Since the WHO's funding depends on donor countries and the fact that African nations and developing countries make up powerful voting blocs, it can't afford to antagonise them.

The job of the WHO chief has always been both the world's doctor and its chief health diplomat.

That's a fine balance but Chan may be too unwilling to administer tough medicine.