Olivia Wise, 16 and Terminally Ill, Inspires With Katy Perry Cover

Since finding its way online in mid-October, a video of terminally ill teen Olivia Wise singing Katy Perry's "Roar" has been seen more than half a million times on YouTube. The video, shot in September in a Toronto recording studio, is a touching document of Wise's spirit and positivity despite having an untreatable brain tumor discovered after suffering a seizure in early 2012.

The video was the idea of Wise's cousin, Jeff Kassel, who enlisted the help of friend Jon Levine, a Canadian producer-songwriter now based in Los Angeles. In it, the 16-year-old from Toronto is seated in a wheel chair while singing in her light but resolute voice. A seriousness covers her until she gets to the line -- "Cause I am a champion, and you're gonna hear me roar" -- when she smiles through the pain.

"You don’t know the half of it when you just hear a girl singing," Kassel tells the Toronto Star, "And she's sitting in a chair and she still looks beautiful, and she still seems vibrant and full of life, and you don’t know what she’s been battling and what she’s going through."

One of the many people touched by Wise's performance has been Perry herself, who sent the teen a rave review of her own.

"It was very moving and it sounded great," Perry says in a video posted late last month. "I love you, a lot of people love you, and that's why your video got to me, and it moved everybody that saw it… Thank you so much. Keep roaring."

Wise's family says that since recording the song, the teen's health has greatly deteriorated and that she is now drifting in and of consciousness. "She's at the end," Kassel told CNN. "She is still conscious at times and taking it all in."

The Liv Wise Fund, started in her honor to support brain tumor research, has raised over $43,000 towards its $150,000 goal. You can donate here.