The investigation of an Oregon zoo has uncovered an outbreak of tuberculosis affecting at least seven people and three elephants, according to data recently published in MMWR.

The investigation began in May 2013 when a routine annual trunk-wash sample culture yielded Mycobacterium tuberculosis. In light of previous documentation of bidirectional M. tuberculosis transmission, the local health department identified and evaluated close and casual contacts of the elephant using either tuberculin skin test (TST) or interferon gamma release assay (IGRA).

Six close contacts with no history of positive TST or other risk factors for TB were diagnosed with latent TB, while no positive TST or IGRA results were obtained from casual contacts.