Tuberculosis, 2018

In 2018, 172 tuberculosis (TB) cases (3.1 per 100,000 population) were reported. This represents a 3% decrease in the number of cases compared to 2017, when there were 178 cases. The TB incidence rate in Minnesota has typically been lower than the overall rate in the United States, but Minnesota’s rate in the last few years has been higher than the national rate (2.8 per 100,000 in 2018). Despite the higher TB case counts and rates in Minnesota recently, the TB case count has decreased 28% since 2007, when 238 cases were reported, and has remained under 200 since 2009. Four (2%) cases from 2018 died, 1 of whom died due to TB disease.

Twenty-seven (31%) counties had at least 1 TB case in 2018. The majority (70%) of cases occurred in the metropolitan area, primarily in Hennepin (31%) and Ramsey (20%) Counties. Thirty-three (19%) were from the other 5 metropolitan counties. The remaining 30% of cases were reported from Greater Minnesota, representing a 3% increase from 2017. Among metropolitan area counties, the highest TB incidence rate in 2018 was reported in Ramsey County (6.2 per 100,000), followed by Hennepin County (4.3 per 100,000). The TB incidence rate for all Greater Minnesota counties combined was 2.0 per 100,000.

The largest group of new TB cases was the 25-44 year age group at time of diagnosis (42%), followed by cases 65 years and older (18%). Two percent of new cases were <5 years of age when they were diagnosed.

Most (78%) TB cases were identified only after seeking medical care for symptoms of disease. Various targeted public health interventions identified the majority of the remaining 22% of cases. Such case identification methods are high priority core prevention and control activities, and include contact investigations (6%) and follow-up evaluations of individuals with abnormal findings on pre-immigration exams where infectious TB disease had been ruled out (3%). An additional 9% were identified through other screening (e.g., other immigration medical exams, employment screening, other targeted testing for TB). Six (3%) cases were diagnosed with active TB disease incidentally while being evaluated for another medical condition.

TB incidence is disproportionately high among racial and ethnic minorities in Minnesota, as it is among cases reported nationally. In 2018, 12 cases occurred among non-Hispanic whites, a case rate of 0.3 per 100,000. In contrast, among non-Hispanic persons of other races, 97 cases occurred among blacks/Africanborn persons (24.9 cases per 100,000), and 52 among Asian/ Pacific Islanders (17.5 cases per 100,000). Ten cases were Hispanic persons of any race (3.3 cases per 100,000). One case was reported as multi-racial. The majority of Hispanic (60%), Asian (90%), and black cases (91%) were non-U.S. born.

In 2018, the percentage of TB cases in Minnesota occurring in persons born outside the United States was 83%, compared to 70% of TB cases reported nationally. The 142 non U.S.-born TB cases represented 30 different countries of birth; the most common region of birth among these cases was Sub-Saharan Africa (61% of non-U.S. born cases), followed by South/ Southeast Asia (26%), East Asia/ Pacific (7%), and Latin America (including the Caribbean) (4%). Patients from other regions (North Africa/Middle East, and Eastern Europe) accounted for the remaining 1% of cases (Figure 7).

Individuals in other high risk groups comprised smaller proportions of the cases. Note that patients may fall under more than one risk category. Twenty-seven percent occurred in persons with certain medical conditions that increase the risk for progression from latent TB infection to active TB disease (e.g., diabetes, prolonged corticosteroid or other immunosuppressive therapy, end stage renal disease). The next most common risk factor was substance abuse (including alcohol abuse and/ or injection and non-injection drug use) during the 12 months prior to their TB diagnosis (6%). Three percent of cases were coinfected with HIV. Two percent reported being homeless during the 12 months prior to diagnosis, 2% were residents of long-term care facilities, and 1% were in a correctional facility at time of diagnosis.

By site of disease, 47% of cases had pulmonary disease exclusively. Another 14% had both pulmonary and extrapulmonary sites of disease, and 38% had extrapulmonary disease exclusively. Among the 90 patients with an extrapulmonary site of disease, the most common sites were lymphatic (51%), followed by musculoskeletal (18%). Extrapulmonary disease is generally more common among persons born outside the United States, as seen in cases reported nationally as well as in Minnesota. Fifty-six percent of non U.S.-born cases in Minnesota had at least one extrapulmonary site of disease, compared to only 33% of U.S.-born cases.

Of 130 culture-confirmed TB cases with drug susceptibility results available, 25 (19%) were resistant to at least one first-line anti-TB drug (i.e., isoniazid [INH], rifampin, pyrazinamide, or ethambutol), including 16 (12%) cases resistant to at least INH. There were 7 new cases of multidrug-resistant TB (MDR-TB, or resistance to at least INH and rifampin) reported in 2018, making up 5% of culture-confirmed cases.

• For up to date information see>> Tuberculosis (TB)
• Full issue>> Annual Summary of Communicable Diseases Reported to the Minnesota Department of Health, 2018