Donald trump was given an experimental drug as a precautionary measure and taken to walter reed military hospital on friday, after developing a fever following his diagnosis with covid-19.

The decision to move mr trump to the medical centre in bethesda, maryland, came after the white house doctor said in a memo that the us president was given an infusion of an experimental antibody cocktail manufactured by regeneron pharmaceuticals, a biotech company.

Im going to walter reed, mr trump said in a video posted on twitter after his arrival at the hospital. i think im doing very well, but were going to make sure things work out. he added that his wife melania, who also tested positive for coronavirus, is doing very well.

Mr trump, wearing a mask and dressed in a navy suit and blue tie, walked from the white house residence to board marine one, the presidential helicopter, without any assistance early friday evening.

He disembarked unassisted upon arrival at walter reed, the hospital where us presidents historically receive medical checks and treatment.

White house doctors have not briefed the media, which has sparked criticism that the administration was not being transparent.

One person familiar with the situation said the white house had not briefed top republicans in the senate about the state of mr trumps health. lawmakers were left to analyse the video of mr trump walking out of the white house to get an indication about his condition.

One democratic congressman who has spoken to the party leadership said nancy pelosi, the speaker of the house of representatives, and other top democrats had not been briefed by the white house on the state of mr trumps health.

Shortly before mr trump flew to walter reed, sean conley, the white house physician, said in a memo that the president was fatigued.

Mark meadows, white house chief of staff, had said on friday morning that mr trump was very energetic. the white house also said mr trump had mild symptoms, but the news channel cnn reported later that he had a fever.

When dr conley early on friday revealed that the president tested positive, he had said mr trump and his wife melania would stay in the white house during their convalescence.

Kayleigh mcenany, white house press secretary, said mr trump was moved to walter reed out of an abundance of caution based on recommendations from his medical team. she said he would work from the hospitals presidential offices for the next few days.

President trump remains in good spirits, has mild symptoms and has been working throughout the day, ms mcenany added.

John bolton, the former national security adviser, said on cnn that while it was unsettling to see mr trump leave the white house, precautionary measures were more likely to be taken in the case of a president.

The president was tested for covid-19 on thursday evening after hope hicks a close aide who accompanied mr trump to the presidential debate in ohio this week contracted the virus.

Regeneron said the white house doctor applied for permission to use the antibody cocktail therapy which has not even been approved by regulators on an emergency basis on compassionate use grounds.

Joe biden, the democratic presidential nominee who leads mr trump in the polls, sent his best wishes to his republican opponent, and urged americans to wear masks to protect other people during the pandemic.

This is not a matter of politics. it is a bracing reminder to all of us that we take this virus seriously, mr biden said. so be patriotic. its not about being a tough guy. its about doing your part.

The biden campaign also took a decision to stop airing negative political ads for the time being, according to a campaign official.

The white house has not explained why mr trump received an experimental drug. in early-stage clinical trials, it has been shown to cut the level of the virus and hospital stays when administered early.

Dr topol said the regeneron cocktail was the latest and greatest but said that while it appeared to be safe, we dont know for sure yet.

Shares in regeneron, which plans to discuss the drug with regulators soon, rose 3.4 per cent in after-hours trading to $564.80.

Eric topol, director of the scripps research translational institute who follows covid-19 studies, said he would not have expected mr trump to be admitted to hospital so soon if his symptoms were mild.

However, bob wachter, chair of the department of medicine at the university of california, san francisco, said it could not be assumed that mr trumps condition was deteriorating significantly just based on his hospitalisation.you have to assume that the threshold for taking him to hospital is lower than it would be for an average person, he said.

Dr conley said mr trump was also taking zinc, vitamin d, melatonin, famotidine an antacid and aspirin. he said mrs trump had a mild cough and headache.

Additional reporting by mamta badkar in new york

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