The second confirmation of the virus is believed to be a "rebound" experienced by some patients, Dr O'Connor said.
It is something that can be experienced by patients who have been treated with an anti-viral medication called Paxlovid - the drug the president received.
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In a tweet, Mr Biden said two positive tests in close succession can happen to a "small minority of folks".
He added: "I've got no symptoms but I am going to isolate for the safety of everyone around me.
"I'm still at work, and will be back on the road soon."
The president had tested negative for the last four days, Dr O'Connor said.
Given Mr Biden's lack of symptoms, there is no plan to reinitiate treatment, the medic added.
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0:22
21 July: 'Keep the faith': Biden on his diagnosis
Mr Biden's diary includes a trip to Michigan on Tuesday to promote new legislation to boost the semiconductor industry - a visit announced earlier on Saturday.
After his initial positive test, the White House said the president was continuing to carry out his duties "fully".
Multiple members of the Biden administration and other senior figures in Washington have tested positive for the virus in recent months, including vice-president Kamala Harris, House of Representatives speaker Nancy Pelosi and Attorney General Merrick Garland.
Thousands of protesters have breached Iraq's parliament for a second time this week.
Followers of influential Shia cleric, Muqtada al-Sadr, are demonstrating against efforts by Iran-backed political groups to form the next government.
Security forces deployed tear gas and sound bombs in a bid to prevent people from entering the parliament building in the capital Baghdad.
But demonstrators used ropes to pull down cement barricades leading to the gate of the Green Zone - which is home to official buildings and foreign embassies.
At least 60 people have been injured in the clashes on Saturday, which saw an expected parliament session cancelled.
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Demonstrators occupied the parliament floor and held aloft the Iraqi flag and posters of Mr al-Sadr.
The protests erupted as Iraq continues to face political deadlock, with ordinary people suffering most as a result of the stand-off.
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Mr al-Sadr's party came first in a general election in October but fell short of a majority. Nine months later, no official government has been formed.
The party left talks in June after failing to form a government without Shi'ite rivals - mainly backed by Tehran.
The withdrawal handed the Coordination Framework bloc, led by Iran-backed Shi'ite parties and their allies, the majority necessary to move forward.
Image:Protesters inside the parliament building in Iraqi capital, Baghdad. Pic: AP
Mr al-Sadr insisted any new government should be free of foreign influence and corruption that has plagued Iraq for decades - and has vowed civil unrest if he does not approve of the new regime.
One person among the crowds, Raad Thabet, 41, said: "We came today to remove the corrupt political class and prevent them from holding a parliament session, and to prevent the framework from forming a government.
"We responded to al-Sadr's call. We will go to the Green (Zone). No matter the cost."
Another protester, Abu Foad, said: "We are calling for a government free from corruption and those are the demands of the people."
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0:41
Protesters and police clash in Iraq
Image:Protesters gather on a bridge leading to the Green Zone area in Iraqi capital, Baghdad. Pic: AP
The political stalemate is exacerbated by the fact Mr al-Sadr's loyalists are involved in running the country and hold powerful positions within Iraq's ministries and state organisations.
Caretaker prime minister Mustafa al-Kadhimi called on protesters to "immediately withdraw" as he urged people to show calm and restraint.
A statement posted on his official Twitter account on Saturday said Mr al-Kadhimi had "directed security forces to protect the demonstrators, and called on the demonstrators to remain peaceful in their movement, not to escalate, and to abide by the directives of the security forces whose goal is to protect them, and to protect official institutions."
Image:A demonstrator waves an Iraqi flag as people gather near the Green Zone area in Baghdad Pic: AP
Image:A protester holds a poster depicting Muqtada al-Sadr on a bridge leading towards the Green Zone area Pic: AP
Image:A man waving the Iraqi flag during the protests. Pic: AP
Why is Iraq in political deadlock?
The selection of a president and the prime minister has been a painfully slow process since Saddam Hussein was toppled by the US-led invasion of Iraq in 2003.
A former CIA analyst who debriefed the captured leader warned that had Hussein stayed, Islamic State may not have gained ground in Iraq.
In March this year, Iraq's parliament failed again to vote for a president after a boycott by Iran-backed groups.
Mr al-Sadr had hoped Rebar Ahmed Khalid, veteran Kurdish intelligence official and interior minister of Iraq's autonomous Kurdistan region in the north, would be elected.
But just 202 members of 329 attended the vote - less than the minimum two-thirds required to choose a new president - while 126 officials boycotted the session.
The jackpot grew to such an astronomical figure after 29 consecutive draws without a winner.
The jackpot is the biggest lottery prize in nearly four years.
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The winner can either claim the $1.28bn prize in the annuity option, which spreads the amount over 30 annual payments, or a cash option for an estimated $747.2m (£613.3m). Nearly all jackpot winners choose the cash option.
Those who opt for the full prize could eventually afford to buy the world's largest yacht twice over. The 590ft megayacht belongs to Sheikh Khalifa bin Zayed al Nahyan, President of the United Arab Emirates.
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The odds of winning the jackpot were one in 302.5 million.
At least 16 people have died due to historic flash flooding caused by torrential rains in eastern Kentucky, the US state's governor has said.
Kentucky Governor Andy Beshear said that he expects the death toll to continue to rise.
President Biden declared the floods "a major disaster" on Friday and ordered federal aid to help with local recovery efforts.
Among the dead are six children, including a one-year-old.
More than 23,000 people are also without power in the state.
After an aerial tour with the National Guard, Mr Beshear said the flood "is by far the worst" he has seen. Parts of cities are submerged under water, and some areas are impassable, he said.
The flash flooding came after heavy rains earlier this week. Hundreds of homes in Kentucky have been wiped out because of the floods, the governor said.
Some areas reported receiving more than eight inches, or 20 centimetres, of rain in a 24-hour period.
Flood warnings remained in effect as of midday Friday in eastern Kentucky, as well as for parts of Tennessee and West Virginia.
Rivers in the region are expected to crest throughout the weekend, and a risk of more dangerous flash flooding remained possible throughout Friday, the US National Weather Service said.
More rainfall is expected early next week, Mr Beshear said, urging people to have a safety plan in place.
Representatives from the US Federal Emergency Management Agency (FEMA) arrived Friday morning to assist local rescue efforts.
Mr Beshear said it's unclear yet exactly how many people are affected or missing. Some areas have been difficult to reach due to damaged portions on 28 state roadways.
On Friday afternoon, the governor confirmed that the bodies of four young siblings were among those who were found - the oldest an eight-year-old and the youngest a one-year-old.
The children's cousin - Brittany Trejo - told the Lexington Herald-Leader that the children and their parents sought shelter at a tree after their home flooded on Thursday.
"They managed to get to a tree and ... held the children a few hours before a big tide came and wash them all away at the same time," Ms Trejo told the paper.
She added the mother and father, who survived, were stranded at the tree for eight hours before help arrived.
Around 50 air rescue operations were conducted on Thursday, along with more than 100 boat rescues. Nearly 300 people have been rescued across the state, with search and rescue efforts ongoing.
"It's going to be a tough couple of days, it's going to be a long rebuild," Mr Beshear said.
At least 16 people have died due to historic flash flooding caused by torrential rains in eastern Kentucky, the US state's governor has said.
Kentucky Governor Andy Beshear said that he expects the death toll to continue to rise.
President Biden declared the floods "a major disaster" on Friday and ordered federal aid to help with local recovery efforts.
More than 23,000 people are also without power in the state.
"We know some of the loss will include children, we may have even lost entire families," Mr Beshear said in a video posted online on Friday morning.
In an update, he said among the dead are an 81-year-old woman and two children.
The flash flooding came after heavy rains earlier this week. Hundreds of homes in Kentucky have been wiped out because of the floods, the governor said.
Some areas reported receiving more than eight inches, or 20 centimetres, of rain in a 24-hour period.
Flood warnings remained in effect as of Friday morning in eastern Kentucky, as well as for parts of Tennessee and West Virginia.
Rivers in the region are expected to crest throughout the weekend, and a risk of more dangerous flash flooding remained possible throughout Friday, the US National Weather Service said.
More rainfall is expected on Monday and Tuesday, Mr Beshear said, urging people to have a safety plan in place.
Representatives from the US Federal Emergency Management Agency (FEMA) arrived Friday morning to assist local rescue efforts.
Mr Beshear said it's unclear yet exactly how many people are affected or missing. Some areas have been difficult to reach due to damaged portions on 28 state roadways.
In an interview with NBC News, Mr Beshear said this is "by far the worst flooding disaster" he has seen in his lifetime.
"Hundreds of Kentucky families are going to lose everything," he said.
Around 50 air rescue operations were conducted on Thursday, along with more than 100 boat rescues. Nearly 300 people have been rescued across the state, with search and rescue efforts ongoing.
"It's going to be a tough couple of days, it's going to be a long rebuild," Mr Beshear said.
Footage which appears to show Russian soldiers pinning a Ukrainian prisoner of war to the ground before cutting off his genitals has sparked outrage in Ukraine.
Ukrainian MP Inna Sovsun tweeted to say she was banned by Twitter after posting the clip on the social media platform.
Once she had regained access to her account, Ms Sovsun shared a screenshot of her original post with the video blurred.
Sky News has decided not to show any footage or images.
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She had written in her original tweet: "Russian soldier from Chechen battalion Ahmat cut off the genitals of Ukrainian POW (prisoner of war).
"This is what Nazis are doing to Ukrainians.
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"Russia has to pay for it!
"Give Ukraine the weapons we need to stop this nightmare once and for all. The world can't pretend like this isn't happening!"
Ms Sovsun wrote in a follow-up tweet on Friday: "Twitter banned my profile today. Because I posted a video where a Russian soldier castrates a Ukrainian POW.
"@Twitter decided it was too cruel. But this is what happens. And deleting the video won't change that.
"People should know what #Russia is doing!"
The video shows a group of men in Russian camouflage outfits pinning a Ukrainian prisoner of war to the ground.
They are then said to use a box cutter to remove his genitals before showing them to the camera.
'Brutal war crimes' must be investigated
In further footage seen by Sky News, the same prisoner is videoed getting tied up and shot in the head at the same location.
It is not clear when or where the video was filmed.
Ukraine's Ministry of Foreign Affairs condemned the "brutal war crimes", calling on the International Criminal Court to investigate.
"Ukraine strongly condemns the brutal war crimes committed by the servicemen of the Russian Federation against Ukrainian prisoners of war, particularly horrible cases of torture, physical abuse, inhuman treatment, wilfully causing great suffering or serious injury to body or health and wilful killing of Ukrainian prisoners of war," the department said in a statement.
"Minister of Foreign Affairs Dmytro Kuleba calls on the international community to condemn the brutal violation of international law by the Russian Federation and to immediately recognize Russia as a terrorist state
"He emphasised that any delay in this decision will only encourage Russia to commit further crimes and inhumane acts."
War crimes allegations against Russia continue to mount
Since the invasion of Ukraine began in February, Russia has been accused of committing thousands of war crimes.
The International Criminal Court has described Ukraine as a "crime scene", sending its largest ever team to investigate.
A Russian former TV journalist has been found guilty of discrediting the country's armed forces after she condemned the Kremlin's actions in Ukraine on social media.
Appearing at an administrative court in Moscow, Marina Ovsyannikova labelled the proceedings against her as "absurd".
"The evidence confirms Ovsyannikova's guilt. There is no reason to doubt its authenticity," the judge said after a short hearing.
The judge found her guilty of the posts on social media and fined her 50,000 roubles (£677) under a law passed in March, soon after President Vladimir Putin launched what he calls his "special military operation" against Ukraine.
At the time she was the editor of the Vremya nightly news programme.
She was fined for flouting protest laws at the time and later took to social media to say that those responsible for Russia's actions would find themselves in the dock before an international tribunal.
After storming the live TV set in March, Ovsyannikova told Reuters she was scared for her safety and that of her children but she has no plans to leave Russia.
