Public Health Response to Tuberculosis Outbreak among Persons Experiencing Homelessness, Minneapolis, Minnesota, USA, 2017-2018

Abstract

Tuberculosis (TB) is a greater risk for populations experiencing homelessness. When a TB exposure occurs in a homeless shelter, evaluation of contacts is both urgent and challenging. In 2017, local public health workers initiated a response to a TB outbreak in homeless shelters in Minneapolis, Minnesota, USA. In this contact investigation, we incorporated multiple techniques to identify, evaluate, and manage patients, including the concentric-circle method to characterize amount of contact, identifying the most frequent sites of sporadic medical care, using electronic medical records, and engaging with medical providers treating this population. Of 298 contacts evaluated, 41 (14%) had latent TB infection and 2 had active TB disease. Our analysis indicated a significant relationship between duration of exposure and positive TB test result (p = 0.001). We encourage local public health departments to expand beyond traditional contact tracing techniques by leveraging partnerships and existing systems to reach contacts exposed in shelters.

Keywords: Minneapolis; Minnesota; Mycobacterium tuberculosis; USA; bacteria; concentric-circle approach; contact tracing; homeless persons; homeless shelters; outbreak; persons experiencing homelessness; public health response; respiratory infections; tuberculosis; tuberculosis and other mycobacteria.

Figure 1

Whole-genome sequencing map of Hennepin County tuberculosis (TB) case cluster, Minneapolis, Minnesota, USA, including cases identified in Texas, USA, in 2016. A) 2008–2016 case cluster, which included 18 cases; B) updated 2008–2018 case cluster, totaling 24 cases. Isolates with the same genome sequence are displayed together in 1 node. Nodes are connected by lines proportional in length to the number of single-nucleotide polymorphism differences between isolates (n = 1, for all). No epidemiologic link to Minnesota was identified for the cases in Texas. Node A contains 10 cases diagnosed during 2008–2015 and the most recent common ancestor reference point. In panel A, node B contains 4 cases diagnosed during 2014–2016, and in panel B, node B contains 8 cases diagnosed during 2014–2018.

Figure 2

Chest radiograph findings and TB test results of contacts for case-patients 1–3 of Hennepin County TB case cluster, Minneapolis, Minnesota, USA, 2017–2018. At the initial screening, contacts were evaluated by either an interferon-γ release assay or a tuberculin skin test and recommended to undergo chest radiography. Those with suspected active TB were requested to provide sputum samples for further diagnostics (smear test, Mycobacterium tuberculosis culturing, and interferon-γ release assay). Two contacts were identified as having active pulmonary disease. TB, tuberculosis.