WASHINGTON - President Joe Biden's temperature rose on Thursday evening after he tested positive for the coronavirus but his symptoms have been improving, his physician said Friday, as White House officials signaled that his bout with the coronavirus is likely to be short and mild.

Biden had a temperature of 99.4 degrees Thursday evening, physician Kevin O'Connor said in a letter released Friday, but his temperature had remained normal after he took Tylenol. The president still had a runny nose, fatigue and a dry cough, O'Connor said, and was responding well to the antiviral Paxlovid.

O'Connor said that Biden's voice was "deeper" Friday morning but that the president's pulse, blood pressure, heart rate and oxygen levels were normal. The doctor had said Thursday that he expected Biden to respond favorably to treatment, and he added on Friday that "there has been nothing in the course of his illness thus far which gives me cause to alter that initial expectation."

White House officials continued to stress Friday that the 79-year-old Biden, who is vaccinated and has been boosted twice but remains at higher risk of severe illness because of his age, was continuing to work despite his infection. They have taken great pains to show that Biden is handling a full workload, even if he's being forced to do it in isolation.

The White House had identified 17 people who are considered "close contacts" of the president in the 48 hours before his positive test, White House press secretary Karine Jean-Pierre said Friday. The Centers for Disease Control and Prevention defines that category as people who were within 6 feet of someone with the coronavirus for at least 15 minutes.

The close contacts include senior Biden staffers and members of Congress, but Jean-Pierre declined to name them individually. None of those contacts had tested positive and all are wearing masks, Jean-Pierre said.

In recent months, the president has suggested that Americans can largely go about their normal lives at this point in the pandemic as long as they take reasonable precautions, especially getting vaccinated. Since his positive test result Thursday morning, Biden has sought to model that response himself, isolating but continuing to work.

Biden canceled a planned trip Thursday to Pennsylvania, where he was to talk about crime and policing, and is not expected to travel to Florida on Monday as he was scheduled to do. He is staying in Washington this weekend, forgoing his usual weekend stay in Wilmington, Del., and has nothing on his public schedule.

Biden did appear on video Friday for a virtual meeting with his economic and energy advisers to stress that the price of gas has been falling for weeks.

In that appearance, Biden had a dry cough and his voice was hoarse. "I feel much better than I sound," Biden said. At the end of the event, when a reporter asked how he felt, he gave a thumbs-up.

Shortly after news of his positive test Thursday, Biden tweeted that he was "doing great" and "keeping busy!" He followed that up with a video on Twitter assuring Americans that he was fine, and he posted a picture of himself Friday signing an executive order to increase access to baby formula. Biden wore a KN95 mask in the photo.

While Biden is fully vaccinated and boosted, and his bout of COVID-19 is unfolding in stark contrast with that of President Donald Trump, who contracted the coronavirus a month before the 2020 election, before vaccines were available. Trump, who made a point of taking few precautions against the disease, was rushed to Walter Reed National Military Medical Center, and at one point aides feared he would have to be put on a ventilator.

Biden will isolate at the White House for at least five days, White House officials said, and will remain in isolation until he tests negative.

As a candidate and then president, Biden has taken significant measures to protect himself against the coronavirus. But the highly contagious subvariant BA.5 has been racing across the country, often able to overcome the immunity conferred by vaccines or previous coronavirus infection.

Many in the Bidens' inner circle have contracted the virus, including Vice President Kamala Harris, Biden's sister Valerie Biden Owens, Secretary of State Antony Blinken and chief medical adviser Anthony Fauci.

On Friday, White House coronavirus response coordinator Ashish Jha used much of a press briefing to stress that all Americans have access to the vaccines and treatments that are helping ensure Biden's infection will remain mild. "He's doing better because he's vaccinated, he's boosted and he's getting treatment," Jha said of the president.

Jha told reporters Friday that nearly every COVID-19 death in the United States should be avoidable at this stage in the pandemic.

"We are now at a point, I believe, where we can prevent nearly every COVID death in America," Jha said. "That is a remarkable fact. So if you are vaccinated but have not gotten a booster, this is a really good time to go and get a booster."

Jha urged Americans to make use of the tools that help make coronavirus infections less severe, including Paxlovid. He specifically encouraged those over 50 who have not gotten a booster shot in 2022 to do so.