President Higgins has been leading the tributes to former Galway resident health pioneer Aidan O’Leary who has died suddenly while on holiday with his family.
59 year old Mr O'Leary has been leading the World Health Organisation’s bid to eradicate polio.
President Higgins says Aidan O’Leary "was a wonderful person who dedicated his life to helping those living in the most difficult, war-torn parts of the world".
WHO director general Dr Tedros Adhanom Ghebreyesus described him as an outstanding humanitarian whose passing is a terrible loss for WHO, for the UN and for all of humanity.
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.
Dublin-born Mr O’Leary lived in Galway before relocating to Geneva is survived by his wife Karen and two children Darragh and Eimear as well as a wide circle of family and friends.