M. canetti is rare and seems to be limited to the Horn of Africa, although a few cases have been seen in African emigrants. M. microti is also rare and is seen almost only in immunodeficient people, although its prevalence may be significantly underestimated. Other known pathogenic mycobacteria include M. leprae, M. avium, and M. kansasii. The latter two species are classified as "nontuberculous mycobacteria" (NTM) or atypical mycobacteria. NTM cause neither TB nor leprosy, but they do cause lung diseases that resemble TB. Transmission
When people with active pulmonary TB cough, sneeze, speak, sing, or spit, they expel infectious aerosol droplets 0.5 to 5.0 µm in diameter. A single sneeze can release up to 40,000 droplets. Each one of these droplets may transmit the disease, since the infectious dose of tuberculosis is very small (the inhalation of fewer than 10 bacteria may cause an infection). Risk of transmission
People with prolonged, frequent, or close contact with people with TB are at particularly high risk of becoming infected, with an estimated 22% infection rate. A person with active but untreated tuberculosis may infect 10–15 (or more) other people per year. Transmission should occur from only people with active TB – those with latent infection are not thought to be contagious. The probability of transmission from one person to another depends upon several factors, including the number of infectious droplets expelled by the carrier, the effectiveness of ventilation, the duration of exposure, the virulence of the M. tuberculosis strain, the level of immunity in the uninfected person, and others.
Suberosis is a type of hypersensitivity pneumonitis usually caused by the fungus Penicillium glabrum (formerly called Penicillium frequentans) from exposure to moldy cork dust. Chrysonilia sitophilia, Aspergillus fumigatus, uncontaminated cork dust, and Mucor macedo may also have significant roles in the pathogenesis of the disease. Cause
Cork is often harvested from the cork oak (Quercus suber) and stored in slabs in a hot and humid environment until covered in mold. Cork workers may be exposed to organic dusts in this process, leading to this disease. Diagnosis
Chest radiography, high-resolution chest CT, pulmonary function testing, bronchofibroscopy with BAL and transbronchial biopsy, delayed cutaneous hypersensitivity tests, fungal and suberin antigen testing, immediate hypersensitivity specific skin tests, and specific bronchial challenge tests can all be used for diagnosis. Chest radiography can show fine miliary mottling. Obtaining a history of antigen exposure and asking about symptoms (e.g. dyspnea, cough) can also be useful. Treatment
Avoidance of antigen exposure is beneficial. History
Vinte-e-Um Mendes first reported respiratory disease in Portuguese cork workers in 1947 at the Portuguese Medical Reunion. Cancella dAbreu first described the disease in 1955. See also
Hypersensitivity pneumonitis

References
Further reading
Cancella de Abreu, LC (1955) On a special kind of pneumoconiosis: the suberosis [in Portuguese]. Med Contemp 73,235-243


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