Prime Minister Boris Johnson "is fully conscious," Northern Ireland Secretary of State Brandon Lewis has said.
Northern Ireland's political leaders have rallied to offer their support to the Conservative leader.
Mr Johnson, 55, was admitted to intensive care at St Thomas' Hospital in London on Monday evening. Foreign Secretary Dominic Raab is leading he government.
Mr Lewis said the Government was being transparent on the Prime Minister's health and there would be continual updates throughout the day.
"The Prime Minister is fully conscious," he told talkRadio.
"He is the Prime Minister of the country, we have got a strong cabinet, we are all absolutely united. Dom [Raab] as foreign secretary and first secretary of the cabinet is empowered to deputise for the Prime Minister and is doing so and will do an excellent job," he said.
"But we all work together on this and there will be meetings all through today which I will be attending as a cabinet minister which will look at the economic impacts of what we are doing, looking at the health impacts ... how we make sure things like [personal protective equipment] get to where they need to be as we did with five million pieces of PPE for Northern Ireland just yesterday.
"All of that work continues we do that as a team and we are united in doing that and we are all very clear on the direction set by the prime minister that we are determined to live on."
Earlier Cabinet minister Michael Gove said Mr Johnson has received "oxygen support" but had not been put on a ventilator.
He added: "The Prime Minister is someone who has amazing energy, great determination, a desire all the time to make sure that things are moving forward."
In a statement on Tuesday, a No 10 spokesperson confirmed the Prime Minister hasn't been diagnosed with pneumonia. Downing Street said Mr Johnson was stable overnight and "remains in good spirits".
"He is receiving standard oxygen treatment and breathing without any other assistance," they said. "He has not required mechanical ventilation or non-invasive respiratory support."
Northern Ireland Secretary of State Brandon Lewis has said the PM is "fully conscious".
I have been speaking to @JuliaHB1 this morning about all our best wishes for the Prime Minister to have a full & speedy recovery & outlining the govt focus on the health of people across the UK, as well as the duty we all have to help the NHS & #StayHomeSaveLives https://t.co/19nK2tCOkg— Brandon Lewis (@BrandonLewis) April 7, 2020
Northern Ireland's political leaders have offered their support to the Prime Minister.
"On behalf of the Northern Ireland Executive, I send our best wishes to the prime minister," First Minister Arlene Foster tweeted.
"Praying for a full and speedy recovery."
Deputy First Minister Michelle O'Neill added: "Wishing Boris Johnson and all those battling Covid-19 every best wish to a speedy recovery."
Assembly Speaker Alex Maskey, on BBC Good Morning Ulster, said everyone was aware of the dangers the virus posed.
"An awful lot of people are suffering, an awful lot of people's lives are in danger and I certainly would not want to hear of any further danger to the British Prime Minister more than anybody else," he said.
"So I would wish him well and a very speedy recovery and hopefully an end to this coronavirus crisis for all of our citizens across these island and around the world.
"I can only wish everyone well and their families well who have to suffer and endure an horrendous time alongside their loved ones who are very seriously ill."
On behalf of the Northern Ireland Executive, I send our best wishes to the Prime Minister @BorisJohnson— Arlene Foster #WeâllMeetAgain (@DUPleader) April 6, 2020
Praying for a full and speedy recovery.
Wishing Boris Johnson and all those battling Covid 19 every best wish to a speedy recovery.— Michelle OâNeill (@moneillsf) April 7, 2020
News emerging this evening that the @10DowningStreet is in ICU.— Naomi Long MLA (@naomi_long) April 6, 2020
My thoughts are with @BorisJohnson and his family and friends this evening at this truly worrying time.
Hope that he makes a speedy and full recovery. https://t.co/M6CEi27AwY
My thoughts are with @BorisJohnson tonight. I hope he makes a full and speedy recovery.— Colum Eastwood (@columeastwood) April 6, 2020
Our thoughts & prayers are for @BorisJohnson & all those suffering - but he is in the good hands of our brilliant @NHSuk - we wish him, and all victims, a swift recovery @uuponline @BrandonLewis @markdevenport https://t.co/7BdAOfIjbY— Steve Aiken OBE (@SteveAikenUUP) April 6, 2020
@BorisJohnson is in our thoughts tonight. We wish him a speedy recovery and a rapid return to health— Leo Varadkar (@LeoVaradkar) April 6, 2020
Taoiseach Leo Varadkar and Irish Foreign Affairs Minister Simon Coveney also offered their best wishes and hoped the PM made a full recovery.
UUP leader Steve Aiken added: "Our thoughts and prayers are for Boris Johnson and all those suffering - but he is in the good hands of our brilliant NHS. We wish him, and all victims, a swift recovery."
SDLP leader Column Eastwood said his thoughts were with the PM.
"I hope he makes a full and speedy recovery," he added.
Alliance leader Naomi Long said her thoughts and prayers were with Mr Johnson and his family and also hoped he made a speedy recovery. She said it was a "truly worrying time".