WASHINGTON, Oct. 8 (Xinhua) -- Remaining infected with COVID-19, U.S. President Donald Trump returned to the Oval Office at the White House on Wednesday.

He was received by the news that General Gary Thomas, the assistant commandant of the Marine Corps, has contracted COVID-19, the latest example of the freewheeling transmission of the coronavirus among U.S. high-ranking officials.

Thomas, the second highest-ranking officer in the U.S. Marine Corps, is "experiencing mild symptoms, but otherwise is feeling well," according to a Marine Corps press release.

He was diagnosed days after attending a Pentagon meeting on Friday with the Coast Guard's vice commandant, Admiral Charles Ray, who on Tuesday tested positive for COVID-19, and members of the U.S. Joint Chiefs of Staff, who entered self-quarantine upon Ray's positive result.

While exactly how Ray contracted the virus is unclear, media observed that he attended an event celebrating Gold Star families on Sept. 27, hosted by the first couple at their residence.

Added to the president's list of troubles is the growing number of infections in his orbit. His top aide Stephen Miller tested positive on Tuesday, joining the growing COVID-19 cluster at the White House, as have Trump's press secretary Kayleigh McEnany and his re-election campaign manager Bill Stepien.

According to an internal government memo leaked to the press Wednesday, as many as "34 White House staffers and other contacts" have tested positive for COVID-19, more than previously known.

Others caught up in the White House outbreak include the president's counselor Hope Hicks, Republican Senator Thom Tillis, Mike Lee and Ron Johnson, Trump's former campaign manager Kellyanne Conway and former New Jersey Governor Chris Christie.

Vice President Mike Pence and 2020 Democratic vice presidential nominee Kamala Harris both tested negative for COVID-19 on Wednesday before they exchanged tirades in their vice president debate, in which Harris hammered Trump's handling of the pandemic.

Democrats are demanding more information and transparency from the White House around details of recent events that may have led to the infection of Trump and others.

"The Trump White House's opaque, secretive handling of its super-spreader event is a public health threat," Senate Minority Leader and New York Democrat Chuck Schumer tweeted. "The outbreak which hospitalized Pres. Trump and infected numerous WH staff, 3 Senators, and more has yet to be fully contained."

Announcing his positive test result last week, Trump spent three days in a military hospital for treatment and returned to the White House on Monday.

Trump tweeted on Tuesday morning he felt "great" and looked forward to the next presidential debate with 2020 Democratic presidential nominee Joe Biden in mid-October.

Hours earlier, Republicans again sought to downplay COVID-19 by comparing it to a flu, which was later hidden by Twitter behind a label stating that it violated its rules "about spreading misleading and potentially harmful information" related to the virus.

COVID-19 has infected more than 7.5 million individuals and killed some 211,000 in the United States.