The 33-year-old British actress said Tuesday on Instagram that Tenn, her 3-month-old son with her partner, comedian Alfie Brown, is hospitalized with COVID-19.
Cave shared a photo of her baby boy in his room at the hospital. British prime minister Boris Johnson reimposed a lockdown Monday in England amid the spread of a new, more transmissible variant of COVID-19.
"I watched the news about lockdown from an isolated room in hospital. Poor baby is covid positive. He's okay and doing well but they are being vigilant and cautious, thankfully," Cave captioned the post. "This strain is super powerful and contagious so I do hope that people take extra care in the coming weeks."
"Really didn't want this to be the start of my families new year. Really didn't want to be back in a hospital so soon after his traumatic birth. Once again I'm in awe of nurses and doctors," she added. "Love and best wishes to everyone."
Anna Shaffer, who played Romilda Vane in the Harry Potter movies, and actresses Faye Marsay and Helen Flanagan were among those to voice their support for Cave in the comments.
"We are all behind you brilliant Bam! Sending so much love to you all," Shaffer wrote.
"Sending you and him loads of love and recovery vibes mate. Xxx," Marsay added.
"Sorry your going through this darling xxx," Flanagan said.
Cave gave birth to Tenn in October. She and Brown have two other children, son Donnie and daughter Margot.
"This has been a very different experience to my first two births... much more humbling, terrifying and out of my control. We are currently in the neo natal unit but he's a strong boy and it's the safest place for him right now," Cave said at the time.
Cave played Lavender Brown in the Harry Potter films. She also portrayed Heather on the Sky One series Trollied and appeared in an episode of Black Mirror in 2017.