'Dancing With the Stars' champ Kaitlyn Bristowe, boyfriend Jason Tartick have COVID-19

"Dancing With the Stars" champion Kaitlyn Bristowe and her boyfriend, Jason Tartick, are battling COVID-19, she shared Thursday.

The former Bachelorette wrote that she and Tartick had been in quarantine so that they could celebrate Christmas with family, though they did see one friend who was being tested daily for her job.

The day after their visit, Bristowe's friend tested positive for COVID-19. On Wednesday, the former reality TV star and Tartick, who also appeared on "The Bachelorette," began to feel ill, he said, adding that their symptoms include fevers and achiness.

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"We just want to let everyone know that we thought we were being safe, but covid is bigger than us," she wrote. "Today, We are thinking of everyone who is spending the holidays alone, anyone who is sick or overcoming something, (as 2020 has taught us to overcome a lot), and all of the healthcare workers who have been away from family, taking care of others for months, and months now. We will be ok!! Be safe and happy holidays!!"

Added Tartick: "You just can never be too cautious and careful. There’s no outthinking this god awful virus, lesson learned."

COVID-19 is a highly transmissible disease, and evidence has indicated that small, indoor gatherings are where it spreads most quickly, according to experts. As a result, the Centers for Disease Control and Prevention has released guidelines advising people to avoid traveling and make their holiday celebrations virtual this year to help stop the spread of COVID-19.

"There is no one silver bullet when it comes to interventions. It's sort of a layered approach," said Dr. John Brownstein, an ABC News contributor, epidemiologist and chief innovation officer at Boston Children's Hospital. "Social distancing and mask wearing ... indoor ventilation, limitations on gatherings ... If people are adhering to these general public health guidelines in sort of the broad sense, they've been really successful at driving transmission down."