WILMINGTON, Del. (CBS/CNN) — Former Vice President Joe Biden and his wife, Dr. Jill Biden, tested negative for COVID-19 on Friday morning, following President Donald Trump’s revelation that he had tested positive for the coronavirus just days after the first presidential debate.

“I’m happy to report that Jill and I have tested negative for COVID. Thank you to everyone for your messages of concern. I hope this serves as a reminder: wear a mask, keep social distance, and wash your hands,” Biden tweeted.

There was no contact from the Trump campaign or the White House to alert the Biden campaign of possible exposure, a senior Biden campaign official who was with the former vice president at the debate said.

The Bidens visited Johnstown, Pennsylvania this week during a campaign train tour that launched in Ohio and made multiple stops in western Pennsylvania.

Biden will still be traveling to Michigan today.

The former vice president tweeted well wishes for Trump and first lady Melania Trump, who also tested positive.

“Jill and I send our thoughts to President Trump and First Lady Melania Trump for a swift recovery. We will continue to pray for the health and safety of the president and his family,” Biden tweeted Friday morning.

Biden’s running mate, California Sen. Kamala Harris, tested negative for coronavirus Thursday “as part of the campaign’s routine testing of principals,” a Biden campaign aide said.

Biden campaign manager Jen O’Malley Dillon sent the campaign’s staff an email Friday morning instructing staffers not to post about Trump’s positive test on social media.

O’Malley Dillon also told Biden’s campaign staff to “rest assured that our campaign staff, in consultation with health experts have continued to take every precaution to protect Vice President Biden, Sen. Harris, their spouses and our staff. The health and safety of the entire team has been, and will remain, our number one priority.”

At Tuesday night’s debate, after Trump’s entourage of family and administration officials entered without masks, a Cleveland Clinic doctor approached Trump’s guests, asked them to wear masks and offered masks to them, according to a reporter who observed what was happening in the room before the debate.

When the doctor, who declined to comment to the press, walked off the floor, a debate hall staffer told her, “That’s all you can do.”

“Why is the Trump family allowed to not wear masks in the debate hall while everyone else follows the rules?” Biden’s granddaughter Naomi Biden tweeted Tuesday night as the debate started.

(©Copyright 2020 CBS Broadcasting Inc. All Rights Reserved.The-CNN-Wire™ & © 2020 Cable News Network, Inc., a Time Warner Company contributed to this report.)