WASHINGTON - US President Joe Biden's COVID-19 symptoms "have improved" after the first full day of treatment, the White House physician said on Friday.

Biden's temperature reached 99.4 degrees Fahrenheit (37.4 degrees Celsius) Thursday evening and was given Tylenol, a fever reducer, according to a memo from Dr. Kevin O'Connor.

"His temperature has remained normal since then," O'Connor wrote, adding that his symptoms remain characterized as runny nose, fatigue, and "loose" cough.

Biden's "voice is deeper" Friday morning and "his pulse, blood pressure, respiratory rate, and oxygen saturation remain entirely normal, on room air," the physician said.

O'Connor noted Biden is "tolerating treatment well" and will continue to take Paxlovid, an antiviral therapy produced by Pfizer and given to patients with COVID-19.

Biden, 79, tested positive for COVID-19 Thursday morning, with "mild symptoms," according to the White House. He has been fully vaccinated and twice boosted.

The US president is isolating at the White House. His aides said he continues to "carry out all of his duties fully during that time."

O'Connor said on Friday that they "will continue to monitor him closely" and keep the White House "updated with any changes in his conditions or treatment plan."