Biden, in a tweet, wished the president and first lady well.

New concerns surfaced on Friday about former Vice President Joe Biden’s possible exposure to COVID-19 following President Donald Trump‘s and first lady Melania Trump’s positive diagnosis.

About eight hours after Trump announced the news by tweet just before 1 a.m. Friday, the Democratic nominee for president tweeted his well wishes to the president and first lady shortly after 9 a.m.

Biden was also being tested for COVID-19 Friday morning, according to his campaign.

The president’s diagnosis comes two days after Trump and Biden spent over 90 minutes facing off on the debate stage in a chaotic and continuous presidential face-off.

Precautions were taken to try to mitigate the dangers of COVID-19 during the debate — the candidates did not shake hands while entering the stage, and spoke from two socially-distanced lecterns. However, Biden, Trump and Moderator, journalist Chris Wallace, did not wear masks during their time on stage.

During the debate Tuesday, the president mocked Biden for his frequent use of face coverings.

“I don’t wear masks like him. Every time you see him, he’s got a mask. He could be speaking 200 feet away from it, and he shows up with the biggest mask I’ve seen,” Trump said of Biden.

Biden and his running mate, Sen. Kamala Harris, are tested weekly for COVID-19, according to the campaign, but the 77-year-old would be considered high risk if he gets the virus given his age, increasing concerns about the risk of infection.

The Biden campaign has drawn a sharp contrast the White House on their strategy surrounding COVID-19, shifting their campaign strategy as the virus ground the country to a halt.

When COVID-19 hit a critical mass in the country in mid-March, the Biden campaign said that it would follow the guidance of public health officials, and moved to a mostly virtual campaign, not holding any in-person campaign events with Biden until June 1.

In recent weeks, Biden’s has undertaken a more aggressive campaign schedule, with travel to key battleground states including Florida, Michigan, and Wisconsin.

The day following the debate, Biden took part in seven campaign stops during his ‘Build Back Better,’ train tour across Ohio and Western Pennsylvania.

Biden was slated to travel to Grand Rapids, Michigan, later Friday, though the Biden campaign has not weighed in on how the news of Trump’s diagnosis will impact Biden’s travel.

With just over one month until Election Day, the Biden campaign was also set to resume in-person canvassing this weekend, dispatching several hundred volunteers in Nevada, Michigan, New Hampshire and Pennsylvania — four key battleground states in the presidential election.

“We’re now expanding on our strategy in a targeted way that puts the safety of communities first and foremost and helps us mobilize voters who are harder to reach by phone now that we’re in the final stretch and now that Americans are fully dialed-in and ready to make their voices heard,” Jen O’Malley Dillon, Biden’s campaign manager, said of the new effort.