The Dancing with the Stars pro, 37, announced the news via Instagram on Sunday night, one day before she was scheduled to return to the ballroom on Monday for her second dance with her celebrity partner, Peloton instructor Cody Rigsby.
Burke confirmed she was "fully vaccinated" with Moderna.
"The PCR test came back, and it came back positive," she said through tears in an emotional video. "I feel so bad for Cody. I feel like I'm letting him down. I just feel like s---, to be quite honest. And it's so overwhelming because it's Sunday, and the show's tomorrow."
"I figured I should let you guys know since I've been as open and as real and vulnerable as I could be here," she continued. "I just hope I didn't spread it. For those of you who don't think COVID is a real thing, it's f------ real, dude. So I have to quarantine for 10 days and I've been ordered to stay home … I'll be in bed. I can't believe this happened."
It's unclear at this time what Burke's diagnosis will mean for Rigsby's fate on the show. ABC did not immediately respond to PEOPLE's request for comment.
Burke and Rigsby made their debut during the season 30 premiere of DWTS last week, performing the tango to "Physical" by Dua Lipa. The pair earned a score of 24 out of 40 from judges Len Goodman, Bruno Tonioli, Carrie Ann Inaba and Derek Hough.
ABC/Maarten de Boer
"So excited to finally reveal my partner @codyrigsby!!" Burke posted after the show. "Tonight was unreal, thank you guys for all of the support — we are just getting started and we can't do it without our #boocrew!"
Rigsby also gushed, "Can we talk about @cherylburke?!? How amazing is my @dancingabc partner?"
Earlier this month, Burke opened up about the toll her professional dancing career has taken on her body and mind during an appearance on The Tamron Hall Show.
"You know as a dancer, especially as a woman, our career, it doesn't last very long. The fact that I'm 37 and still sambaing out there and shimmying is pretty unheard of," Burke said. "I'm not in the competitive level anymore, but still I also have to understand that I have arthritis in my body, you know, like, the pounding and pounding and pounding. [I'm] technically leading our sports players or whoever we're dancing with, right?"
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Burke said that the desire to start a family with husband Matthew Lawrence, as well as the impact of pro dancing on her mental health, have made her consider saying goodbye to the ballroom.
"I also have body dysmorphia that I deal with as well that comes with the business that also came even before I moved here to Los Angeles. So there's all that that I have to deal with," she continued. "Then I have to think about — okay it's not just me now it's me and my husband, and what do we want for our future?"
She concluded, "I do know in my heart, I feel like 24 seasons is a huge accomplishment and I am grateful for that experience, but I'm not like these other girls who just had babies and can just bounce back. I know my body, but I also, more importantly, know my own mental health and if I have this body image issue that I'm dealing with, again, if this [points to her head] is not okay I can't perform."
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Breakthrough cases — COVID-19 infections that occur in people who have been fully vaccinated against the virus — are rare, but possible and expected, as the vaccines are not 100% effective in preventing infections. Still, vaccinated people who test positive will likely be asymptomatic or experience a far milder illness than if they were not vaccinated. The majority of deaths from COVID-19 — around 98 to 99% — are in unvaccinated people.