Live updates: follow the latest news on Covid-19 variant Omicron
US President Joe Biden has tested negative for Covid-19 after close contact with a staffer tested positive for the virus, the White House said on Monday, as the country is dealing with a surge fuelled by the highly contagious Omicron variant.
"On Monday morning, a mid-level staff member, who does not regularly have contact with the President, received a positive result for a Covid-19 test," White House press secretary Jen Psaki said in a statement.
"Three days earlier, on Friday, that staff member had spent approximately 30 minutes in proximity to the President on Air Force One...
"This staff member is fully vaccinated and boosted, and tested negative prior to boarding Air Force One, as is required for everyone traveling with the President."
Mr Biden tested negative with an antigen and PCR test in the days following, and will be tested again on Wednesday, Ms Psaki said.
On Tuesday, he is scheduled to address the country on the current surge, where Omicron has become the dominant strain in the US.
Vice President Kamala Harris also tested negative after being in close contact with a staffer who tested positive for Covid, her office said on Wednesday night.
Meanwhile, some US leaders are testing positive for Covid-19 as the country faces a winter surge in coronavirus cases fuelled by the Delta strain and the highly contagious Omicron variant of concern.
Senator Elizabeth Warren of Massachusetts tweeted that she tested positive for Covid-19, crediting her mild symptoms to the protection of three vaccination doses.
"I regularly test for Covid and while I tested negative earlier this week, today I tested positive with a breakthrough case," she posted on Sunday.
Ms Warren has a personal connection to the virus as her older brother died from Covid-19 when the pandemic hit the US in the early spring of 2020.
"It just feels like something that didn’t have to happen," she told The Atlantic.
Representative Jason Crow of Colorado tweeted that he had arrived from an overseas trip and received a positive Covid-19 test.
Senator Cory Booker of New Jersey, who is also vaccinated and boosted against the virus, shared similar news over the weekend.
While the leaders are well protected, the concern is that an uncontrolled spread will mean more unnecessary illness and deaths.
Vaccination is proven to largely protect against severe illness and death from Covid-19.
Washington state senator Doug Ericksen died on Saturday, weeks after he said he had tested positive for the coronavirus while in El Salvador, though his cause of death wasn’t immediately released.
Ericksen was a former leader of Donald Trump’s campaign in Washington. He also was an outspoken critic of Democratic Governor Jay Inslee’s Covid-19 emergency orders, and had introduced legislation aimed at protecting the rights of people who do not wish to get vaccinated.
Ms Warren was working at the US Capitol last week before the Senate adjourned for the year, CNN reported.
Southwest chief executive Gary Kelly was on Capitol Hill for a Senate hearing on Wednesday last week and tested positive for Covid-19 on Friday.
Mr Kelly testified at the time that he believed face masks were unnecessary, although science shows they cut down the spread and infection of the virus.
Republicans are less likely to get vaccinated against Covid-19, but on Sunday former president Donald Trump said he received a booster dose, in an event with former Fox News host Bill O'Reilly on Sunday.
"Both the president and I are vaxxed and did you get the booster?” Mr O’Reilly asked.
Mr Trump responded with a "yes".
Some people in the audience started to boo and he said, "Don't, don't, no."
It is a stark change from when Mr Trump said in August that he thought booster doses were not necessary.
"The whole thing is just crazy," he told Fox News. "You wouldn’t think you would need a booster. You know, when these first came out, they were good for life.”
Ms Psaki was asked about a potential partnering with Mr Trump in an effort to get more Americans to take the jab. Though she doesn’t see that happening, she said that it is a good thing that the former president is communicating accurate information, as opposed to telling people that drinking bleach can kill the virus.
“I think we believe that, you know, the former President being out there and stating what is factually accurate about the efficacy of vaccines, of getting boosted — which he recently did, of course — is a good thing,” said Ms Psaki.
“But certainly, we would applaud — and have — the former President’s comments.”
Senator Chris Coons said on Thursday that he tested positive for Covid-19, making him the 10th member of Congress to contract the virus in December.
This month alone seven House of Representatives members have tested positive for Covid-19.
New York Times reporter Maggie Haberman tweeted a letter she received from Mr Trump on his comments over the weekend, where he wrote "must tell the truth... millions of lives worldwide saved".