Ireland's Chief Medical Officer Dr Tony Holohan is stepping away from his role.
During an emotional statement on Thursday, he revealed his wife is receiving palliative care.
He also asked for respect for his family’s privacy at this time.
"From today I'll be taking time out from all of my work commitments to be with my family", he said.
"My wife Emer was diagnosed with multiple myeloma - a form of blood cancer - in 2012.
"She's had a number of difficult years with her disease and was admitted for palliative care last Saturday.
"And I now want to give my energy, attention and all of my time to Emer and to our two teenage children, Clodagh and Ronan."
He has spoken to Taoiseach Micheál Martin and Health Minister Stephen Donnelly, who he said "kindly offered their support and best wishes to both of us".
He also confirmed that Dr Ronan Glynn has been appointed Acting Chief Medical Officer, and will chair the COVID-19 press conferences going forward.
"As a husband and father, and as a public health doctor, I'm conscious that we've been through tough times together over the last number of months.
"And many families across the country have been affected by the course of COVID-19, suffering pain and the loss of loved ones.
"I hope we can all remain working together to continue to stay vigilant, to keep our social distance and take personal responsibility for our own health in the first instance - as well as looking after our family members, friends and those we care about most".
From today, I will be taking time out from all of my work commitments to be with my family.
I would like to thank everyone for their support, understanding and respect for my family’s privacy and would wish that to continue.
Continue to stay vigilant and look after each other. pic.twitter.com/aNfi88c1Jo
— Dr Tony Holohan (@CMOIreland) July 2, 2020
In a statement, Taoiseach Micheál Martin said: "I would like to thank Dr Holohan on behalf of myself and the people of Ireland for helping to guide this country through the COVID-19 emergency.
"His work, experience and briefings helped people to understand the gravity of the situation facing us, while his calmness reassured us that if we followed the guidelines and advice we would overcome these great challenges together."
"Every home in Ireland has come to know Dr Tony Holohan.
"His leadership during the pandemic has given us all confidence that the decisions being made are based on solid public health advice.
"As a country we owe him and his family a great debt of gratitude".
Health Minister Stephen Donnelly added:"I want to express my heartfelt support and that of Government for Dr Holohan and his family, and ask that their privacy be respected.
"It's important they have this time together.
"I also want to thank Dr Holohan for the leadership and extraordinary commitment and professionalism he has shown throughout the COVID-19 pandemic.
"We are fortunate to have such leadership, and to have the work, expertise and dedication of the National Public Health Emergency Team.
"That team has worked day and night since this pandemic started and it brought us to where we are now with Dr Holohan's leadership.
"Continuity in that work is vital and will be guaranteed with the leadership of Dr Ronan Glynn, who has been deputy chief medical officer at the Department of Health for several years.
"Dr Glynn has been sitting at Dr Holohan's side here every evening, speaking to the public and speaking to the media.
"I look forward to working with Dr Glynn and with the National Public Health Emergency Team as we manage the ongoing impact of this virus".