Doctors do not know when the 64-year-old will come out of the coma as it was not medically induced, Dowse's sister Tracey Dowse wrote on Aug. 7.
"As many of you know I am a private person. So this is hard for me. I am requesting support and prayers be offered me and my sister, and my only immediate family @denisedowse," Tracey said. "She is a vibrant actor and director that should have many years ahead of her. Thoughts, prayers and support are greatly appreciated."
USA TODAY confirmed the social media post is from Dowse's sister Tracey.
Tracey said she is trying to keep her spirits up and support those who need it during this difficult time.
The Mayo Clinic defines meningitis as an inflammation of the fluid and membranes surrounding the brain and spinal cord. Most U.S. cases are caused by "a viral infection, but bacterial, parasitic and fungal infections are other causes," according to their website. Some cases can improve without treatment in a few weeks while others are life-threatening, requiring emergency antibiotic treatment.
Dowse's "90210" co-star Ian Ziering commented on the post, "Sending prayers and hopes for better days ahead."
Dowse is also known for playing Judge Rebecca Damsen on the CBS drama series "The Guardian." Other television credits include "Grey's Anatomy" and "The Resident." Most recently, she played Dr. Rhonda Pine on HBO's "Insecure," which wrapped its final season in December.
Dowse has also appeared in films including "Starship Troopers," "Bio-Dome," "Pleasantville" and "Reign Over Me."
Dowse also directed the film "Remember Me: The Mahalia Jackson Story," starring Ledisi, Corbin Bleu, Keith David and Vanessa Williams. The film, which has not yet been released, is about gospel singer and activist Mahalia Jackson.
This article originally appeared on USA TODAY: Denise Dowse: '90210' actor hospitalized in coma fighting meningitis