Nocardial infections are reported worldwide, but no reliable estimates are available.
Nocardia are distributed in the soil rich in organic matter. Theyare present as transient pathogens in humans.
Nocardia spp. that colonize the normal humans usually do notcause any infection in the same host. Nocardia organisms are exogenous pathogens. The infection is acquired by inhalation of infective aerosols or by penetration through the skin.
Pulmonary and disseminated nocardiosis are increasingly found in the immunocompromised individuals. The infections are much more common in patients with HIV or patients who have received organ, bone marrow, or stem cell transplantation and in patients with cirrhosis, lymphoreticular malignancies, and SLE. The condi-tion is also more common in patients with chronic pulmonary dis-ease, such as emphysema, bronchitis, bronchiectasis, etc.