Nocardiosis is a disease caused by a type of bacteria that is found in the environment, typically in standing water, decaying plants, and soil. These bacterial species belong to the genus Nocardia giving the disease its name.

Nocardia and other related bacteria are considered to be opportunistic pathogens. These are bacteria that infect humans and animals when the conditions are right.

They can cause severe infections in people with weakened immune systems who have difficulty fighting off infections (for example, people with cancer or those taking certain medications such as steroids).

Infection often happens:

When someone breaths in dust that contains the bacteria (lung infection)
When soil or water carrying nocardiosis bacteria gets into the skin through a cut or scrape (traumatic inoculation)

When a hospitalized patient is infected from contaminated medical equipment or from bacteria getting into a wound after surgery (hospital-acquired infection)
Nocardiosis can show up in the body as a skin or lung infection or as an infection that has spread throughout the body (disseminated infection).