A variant of the rustrela virus – related to the wider-known rubella virus which causes a skin rash in humans – called RusV was discovered in a female mountain lion in Douglas County, Colorado last year, according to a study published in the journal, Emerging Infectious Diseases, this month.
The big cat was observed in May 2023 with lesions on her skin and signs of severe muscle weakness in her hind legs. She was also reluctant to get up and had decreased mobility.