Tuberculosis, 2016

In 2016, 168 tuberculosis (TB) cases (3.1 per 100,000 population) were reported. Although this represents a 12% increase in the number of cases compared to 2015 (150), it is a 29% decrease in the number of cases since 2007, when the highest number (238) in the past decade was reported. Unlike most years, Minnesota’s TB incidence rate in 2016 was higher than the national rate of 2.9 cases per 100,000 population. Seven (4%) cases died.

Twenty (23%) counties had at least 1 case in 2016. The majority (77%) of cases occurred in the metropolitan area, primarily in Hennepin (44%) and Ramsey (24%) Counties. Sixteen (10%) were from the other five metropolitan counties. The remaining 23% of cases were reported from Greater Minnesota. Among metropolitan area counties, the highest TB incidence rate in 2016 was reported in Ramsey County (7.4 per 100,000 population), followed by Hennepin County (6.0 per 100,000). The TB incidence rate for all Greater Minnesota counties combined was 1.6 per 100,000 population.

Most (81%) TB cases were identified as a result of individuals seeking medical care for symptoms of disease. Various targeted public health interventions identified a portion of the remaining 19% of cases. Such case identification methods are high priority core prevention and control activities and include follow-up evaluations resulting from abnormal findings on pre-immigration exams performed overseas (7%), contact investigations (5%), and domestic refugee health assessments (2%). An additional 5% were identified through other screening (e.g., other immigration medical exams, employment screening, and other targeted testing for TB). Two (1%) cases were diagnosed with active TB disease incidentally while being evaluated for another medical condition.

TB incidence is disproportionately high among racial minorities in Minnesota as well as in the United States. In 2016, 8 cases occurred among non-Hispanic whites. In contrast, among non-Hispanic persons of other races, 88 cases occurred among blacks (25.0 cases per 100,000), 59 among Asians/Pacific Islanders (21.1 cases per 100,000), and 1 case among American Indians (1.5 cases per 100,000). Twelve cases were Hispanic persons of any race (4.2 cases per 100,000). The vast majority of black (94%) and Asian cases (98%) were non U.S.-born.

In 2016, the percentage of TB cases in Minnesota occurring in persons born outside the United States was 90%, compared to 68% of TB cases reported nationally. The 152 non U.S.-born TB cases reported in Minnesota represented 36 different countries of birth; the most common region of birth among these cases was Sub-Saharan Africa (54% of non U.S.-born cases), followed by South/Southeast Asia (33%), Latin America (including the Caribbean) (7%), East Asia/Pacific (5%), and North Africa/Middle East (1%) (Figure 7).

Individuals in other high risk groups comprise smaller proportions of the cases. Note that patients may fall under more than one risk category. Eighteen percent occurred among persons with certain medical conditions that increase the risk for progression from latent TB infection (LTBI) to active TB disease (e.g., diabetes, prolonged corticosteroid or other immunosuppressive therapy, end stage renal disease). The next most common risk factor was HIV infection (7%). Substance abuse (including alcohol abuse and/ or injection and non-injection drug use) during the 12 months prior to their TB diagnosis was reported for 4% of patients. Four percent reported being homeless during the 12 months prior to diagnosis. Long-term care facility residence at time of diagnosis accounted for 1% of cases.

By site of disease, 57% of cases had pulmonary disease exclusively. Another 10% had both pulmonary and extrapulmonary sites of disease, and 33% had extrapulmonary sites exclusively. Among patients with an extrapulmonary site of disease, the most common sites were lymphatic (62%), followed by musculoskeletal (15%). Extrapulmonary disease is generally more common among persons born outside the United States. In 2016, 46% of non U.S.- born patients had at least one extrapulmonary site of disease, compared to only 19% of U.S.-born cases.

Of 136 culture-confirmed TB cases with drug susceptibility results available, 28 (21%) were resistant to at least one first-line anti-TB drug [i.e., isoniazid (INH), rifampin, pyrazinamide, or ethambutol], including 19 (14%) cases resistant to at least INH. There were 8 new cases of multidrug-resistant TB (MDR-TB; resistance to at least INH and rifampin) reported in 2016, compared to a total of 5 MDR-TB cases in the previous 5-year period (2011-2015).

• For up to date information see>> Tuberculosis (TB)
• Full issue>> Annual Summary of Communicable Diseases Reported to the Minnesota Department of Health, 2016