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BACKGROUND: Prompt diagnosis and treatment of tuberculosis (TB), caused by Mycobacterium tuberculosis, can prevent transmission and death. On April 12, 2013, an adult foreign-born Sheboygan resident (index patient) from a high-incidence country and with a history of being exposed to TB received a diagnosis of pulmonary TB disease (later identified as isoniazid and rifampin resistant, or multidrug-resistant) 8 months after cough onset. Concerned about a prolonged infectious period, we investigated to find and prevent additional cases.
METHODS: We defined a case as TB disease caused by M. tuberculosis with the index case strain genotype in a Wisconsin resident that was diagnosed during May 2012–August 2013; persons with latent TB infection (LTBI) had a positive TB test and an epidemiologic link to a TB patient. To determine factors contributing to transmission and to find contacts, we reviewed medical records and interviewed patients.
RESULTS: Beginning October 2012, the index patient sought medical care for TB symptoms during 9 visits to 7 different providers. Chest radiographs obtained during 3 separate visits were consistent with but not interpreted as TB; TB was first considered during April 2013, approximately 6 months after the first medical visit. Among >700 evaluated contacts, the investigation detected 31 persons with LTBI and 11 secondary TB cases. Among the 12 TB patients, median age was 19 (range: 11–39) years. The index patient had resided in the United States for 19 years.
CONCLUSIONS: Because of delayed diagnosis, the index patient’s prolonged infectious period resulted in extensive transmission. To prevent outbreaks and promptly interrupt TB transmission, clinicians, even in low-incidence settings, should have a high index of suspicion for TB among populations at high risk.