The Irishman leading the World Health Organisation’s bid to eradicate polio has died suddenly while on holiday with his family.

Global Polio Eradication Initiative (GPEI) Director Aidan O’Leary died on Tuesday evening at the age of 59.

WHO director general Dr Tedros Adhanom Ghebreyesus led tribute to Mr O’Leary – describing him as an “outstanding humanitarian”.

“He served tirelessly in the most difficult parts of the world, to help the most vulnerable populations survive and thrive and to end polio,” he said.

“He embodied the ideal of service and solidarity across peoples and borders. His passing is a terrible loss for WHO, for the UN and for all of humanity.”

I'm devastated and heartbroken at the passing of a very dear friend and colleague, Aidan O'Leary, Director of the @WHO Polio Eradication Programme.

Aidan's passing is a shock to all of us, and especially to his family and friends in his native Ireland and around the world. On… pic.twitter.com/p5YXJepTqm

— Tedros Adhanom Ghebreyesus (@DrTedros) August 7, 2024

In a statement, the GPEI said Mr O’Leary was, “a true leader, inspiring us all to strive to attain a better world”.

It noted that he previously served in humanitarian posts in Yemen, Afghanistan, Iraq and Syria.

He also spent time working as Deputy Director of Operations for UN Relief and Works Agency for Palestinian Refugees in the Near East (UNRWA) in Gaza.

“On a personal level, Aidan was an extremely personable, open and gentle friend and colleague.  He will be missed deeply, both on a professional and on a personal level,” it said.

Mr O’Leary is survived by his wife and two children.