Kimberly Guilfoyle, Trump Jr.'s girlfriend, tested positive for COVID-19 over the summer. Trump's chief of staff, Mark Meadows, and other White House aides and members of Congress have also tested positive.
The White House says it constantly tests those around the President and Vice President Mike Pence, but officials often take a lax approach to following US Centers for Disease Control and Prevention's guidelines to wear a mask and social distance. Don Jr. also hosted a densely packed indoor campaign rally days after his father tested positive for the virus.
Trump Jr is one of the most outspoken and aggressive defenders of his father, who is still refusing to recognize his defeat to Democrat Joe Biden in the November 3 presidential election.
Speaking with Fox News' Laura Ingraham last month, Don Jr. downplayed the severity of the pandemic, saying "the number [of new deaths] is nearly nothing because we have gotten control of this".
More than 11 million people have been diagnosed with Covid-19 in the United States.