Sinn Féin President Mary Lou McDonald said that it "hurt to open her eyes" while she was infected with the coronavirus earlier this month.
McDonald announced that she tested positive for the virus on April 13 after a 16-day waiting period and she said that she had never been as sick before in her life.
Now fully recovered, she appeared on the Late Late Show on Friday night to talk about her experience of COVID-19.
"Every part of my hurt. It hurt to open my eyes and my eye sockets ached," she told Late Late Show host Ryan Tubridy.
"I couldn't sustain a conversation. Well, I could, but it took real effort. It literally floored me and I've never experienced anything like it."
She said that the coronavirus felt nothing like a flu and described it as a "horrible, horrible virus."
McDonald, who suffers from asthma, said that she was scared at times during her illness. She said that she began to suffer shortness of breath and stabbing pains in her lungs on Easter weekend said that her husband started to panic over her condition.
"My husband doesn't panic, he's the calmest person on earth, but at that moment he panicked because he thought this was the real deal kicking in.
"My husband doesn't panic, he's the calmest person on earth, but at that moment he panicked".April 24, 2020
She said she can now appreciate how scary the coronavirus is for elderly people or people with an underlying health condition.
"I now fully understand what a frightening prospect this virus is for an older person or anyone with a serious underlying condition."
The Sinn Féin leader has returned to work in the Dáil and also talked politics on Friday's show. She said that there was still a chance that she would be elected Taoiseach.
Fine Gael and Fianna Fáil have agreed to form a coalition government but still don't have a majority in the Dáil. The two parties collectively have 73 seats, seven short of the 80 seats required for a majority.
They have so far failed to entice smaller parties or independent TDs to enter into the coalition and McDonald remains hopeful that Sinn Féin can lead the new government.
"There is some way to go. I don't think it's over yet," she said on Friday night.
Both Fine Gael and Fianna Fáil have ruled out going into government with Sinn Féin and McDonald described their refusal to negotiate with Sinn Féin even during a global pandemic as "shameful".
She said that more has to be done to combat the COVID-19 crisis in Ireland, especially in nursing homes around the country.
"We need to deploy more staff to nursing homes," she said.
There have been around 2,000 confirmed cases of coronavirus in Irish nursing homes and more than 350 deaths. There have been 18,184 confirmed cases of the coronavirus in Ireland and 1,014 deaths as of Friday, April 24, meaning that roughly 35% of Ireland's coronavirus deaths have been in nursing homes.
Nursing homes are currently short-staffed and under-equipped since many nursing home staff have to self-isolate with symptoms of the virus.
Read more: Sinn Féin leader tests positive for COVID-19