In a tweet Sunday, Trump announced that Giuliani had tested positive for COVID-19. He did not provide details on when his personal attorney tested positive or whether he has been showing any symptoms.
Giuliani, 76, did not respond to requests for comment, but thanked a supporter on Twitter who prayed for his health. He also retweeted Trump's tweet about his coronavirus diagnosis.
On Thursday, Giuliani did not wear a mask for several hours while attending a hearing at the Georgia Capitol where several state senators were also without masks, the Associated Press reported.
On Wednesday, Giuliani was maskless for an hourslong committee hearing in Michigan, where he sat next to a number of witnesses who were brought in to make bizarre claims of widespread voter fraud without any evidence.
Jenna Ellis, another member of Trump's legal team, who was sitting next to Giuliani was also not wearing a mask during the hearing which lasted for over four hours.
In a tweet Sunday, Ellis called Giuliani "a tough warrior" and added that their legal team's efforts to overturn the election results "won't be affected" by his diagnosis.
On Monday, Giuliani met a handful of Republican Arizona lawmakers for several hours at a Phoenix hotel as part of an unofficial hearing to cast doubt on the election results, the Arizona Republic reported.
Giuliani tested negative twice immediately preceding his trips to the three states, according to a statement released by the Trump legal team on Sunday night. The statement said that he did not test positive for the virus or experience any symptoms until more than 48 hours after his return.
The team said that no state legislators or members of the press were on the contact tracing list and that other team members who had close contact with Giuliani will follow CDC guidelines on self-isolation and testing.
Giuliani, the former mayor of New York City, revealed in a Bloomberg TV interview in October that he is taking hydroxychloroquine daily, an antimalarial drug which was initially touted as a treatment for COVID-19 but numerous studies have shown to be largely ineffective for sick patients (it's still unclear how effective it is at preventing infection).
Giuliani is the latest in a long list of Trump administration officials and advisers, including Trump himself, to test positive for COVID-19 after actively flouting public health advice to wear masks and practice social distancing.