Epidemiology

Several decades ago, reports estimated the incidence of nocardiosis in the US at 500 to 1000 cases per year.[1] However, due to the increase in the number of immunosuppressed patients since then, the incidence of nocardiosis is also increasing.[2] In one systematic review of populations across the US, Australia, and France, the incidence of nocardiosis in the general population was 0.35 to 0.40 cases per 100,000 person years. The incidence was approximately 140 times greater among individuals with HIV, around 340 times greater among recipients of bone marrow transplants, and almost 3000 times greater in patients with solid organ transplants.[3]

Nocardiosis has been reported worldwide in all ages and races, and it is 2 to 3 times more common in men.[4][5]​​ Pulmonary disease is the most frequent clinical presentation (approximately 50% of cases), and most of the infective organisms are from the former Nocardia asteroides complex.[6] Approximately one third of patients with pulmonary nocardiosis will develop disseminated disease.[7][8]​​ The frequency of Nocardia infections in recipients of solid organ transplants varies between 0.4% and 3%, and have mostly been reported in heart, kidney, liver, and lung transplant recipients.[9][10]​​​ The incidence of nocardiosis is approximately 340-fold higher among bone marrow transplant recipients than in general populations.[3] Primary cutaneous nocardiosis is a rare disease associated with direct inoculation in immunocompetent patients, frequently caused by N brasiliensis.[8][11][12][13][14]

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