About 40 different species of fungus can cause ringworm. They are typically of the Trichophyton, Microsporum, and Epidermophyton types.
These fungi can live on your skin and other surfaces, particularly damp areas. They may also live for an extended period of time as spores in soil.
The fungi can spread to humans in four ways:
Human to human. You can get the infection if you come in contact with a person who has ringworm or if you share personal items, such as combs or towels. The infection is commonly spread among children and by sharing items harboring the fungus.
Animal to human. You can get ringworm after touching an affected animal or even items the animal has come in contact with. Cats and dogs are common sources, but other animals, such as farm animals, can spread the fungi as well.
Object to human. You may get the infection if you come in contact with an object or surface that has it, such as a telephone or the floor of a public shower. These fungi thrive in damp environments.
Soil to human. Humans and animals can get ringworm after direct contact with soil that is carrying the fungi.