US President Donald Trump has told his Twitter followers he is "going well, I think!".
The latest update from Trump on Saturday reads: "Going welI, I think! Thank you to all. LOVE!!!"
It came at the same time as a message from his physician, who said Trump is "doing very well".
"He is not requiring any supplemental oxygen, but in consultation with specialists we have elected to initiate Remdesivir therapy. He has completed his first dose and is resting comfortably".
As the update came from Trump, news also broke that his campaign manager Brad Stepien had tested positive for the illness, the latest in a line of people close to the President to contract the virus.
Earlier on Saturday, Trump was taken to military hospital Walter Reed Medical Centre.
According to CNN sources, Trump was described as being "very tired, very fatigued, and having some trouble breathing".
But Trump said on Saturday in a video posted on Twitter he thinks he's doing "very well".
"I want to thank everybody for the tremendous support. I'm going to Walter Reed Hospital. I think I'm doing very well. But we're going to make sure that things work out," he said.
"The President will be working from the presidential offices at Walter Reed for the next few days," Trump's Press Secretary Kayleigh McEnany confirmed in a statement on Saturday.
Trump has had a fever since Saturday morning, according to CNN.
McEnany said this was "out of an abundance of caution, and at the recommendation of his physician and medical experts."
Earlier, McEnany released a statement from the President's physician Dr Sean Conley, saying he "remains fatigued but in good spirits".
"He's being evaluated by a team of experts, and together we'll be making recommendations to the President and First Lady in regards to next best steps.
"As a precautionary measure, he received a single 8-gram dose of Regeneron's polyclonal antibody cocktail. In addition to the polyclonal antibodies, the President has been taking zinc, vitamin D, famotidine, melatonin and a daily aspirin.
"First Lady Melania Trump remains well with only a mild cough and headache."
Dr Conley added the remainder of the family are well, and all tested negative for COVID-19.
Democratic presidential candidate Joe Biden said he and wife Jill are praying Trump and the First Lady "will make a quick and full recovery."
Biden added: "It's a bracing reminder to all of us that we have to take this virus seriously."
"We have to do our part to be responsible. It means following the science, listening to experts, washing our hands, social distancing. It means wearing a mask in public, it means encouraging others to do so as well."