Sporothrix schenckii is a common soil fungus. When it enters the human body, classically via a thorn prick, it causes Rose-thorn disease. The infection spreads along the lymphatic system from the entry point causing alarming ulcerous skin lesions. Generally the infection dies out within a few weeks or months.

In Rio de Janeiro, the fungus has become endemic in the cat population and a new urban epidemic has arisen, spread by cat claw punctures. Rio is a "perfect storm" of a large, densely populated area with poor housing and sanitation, lack of health services, an elevated proportion of immuno-compromised people and a large population of feral cats.