Results of a study recently published in The Lancet indicated that, although incidence of tuberculosis (TB) is low and continues to decline among children in the United States, the disease disproportionately affects those who are nonwhite, those born in countries or to parents from countries where TB is endemic, or those residing in US-affiliated islands. 

The study included 6072 children and adolescents with verified cases of TB reported between 2010 and 2017 to the National Tuberculosis Surveillance System. Both laboratory and clinical diagnoses were accepted. Of the reported cases, 85% (n=5175) were from the United States, and 15% (n=897) were from US-affiliated islands.

The majority (68%) of children and adolescents with reported TB in the US were born here. Among these children and adolescents, 47% were Hispanic, 25% were black, and 13% were Asian. These three ethnicities also comprised the largest percentages of cases among children and adolescents not born in the United States.

The study included TB rates beginning in 2007, but only included case counts from 2010 onward. Point estimates for incidence rate data were calculated using Poisson models balanced by log population size, which was sourced from the US Census Bureau. Between 2007 and 2017, the incidence rate of TB declined by 47.8% (95% CI, -51.4 to -44.1), from 1.4 to 0.8 per 100,000 person-years. The average rate during this period was 1.0 per 100,000 person-years (8030 cases among 73.6 million youths). Children aged ≤1 year had the highest incidence rates (1.9 per 100,000 person-years; 95% CI, 1.8-2.0).

Those born outside the United States had a 12.9 times higher incidence (95% CI, 12.3-13.5) compared with patients born in the United States; children born in Africa and Oceania showed the highest rates. The birthplace of both the child/adolescent and their parents correlated with different rates of TB. Rates were higher among US-born youths who had at least 1 parent who was not born in the US (1.7 per 100,000 person-years) compared with those whose parents were (0.3 per 100,000 person-years). Further, US-born youths with 2 non-US-born parents had rates of TB 8.5 times higher than those with 2 US-born parents.

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Limitations to these findings included restricted data on international travel, parental birth country, and occurrence of contact with individuals who were not guardians. In addition, there were no data on household crowding, socioeconomic indicators, nutrition, or health insurance

The study researchers concluded that “[although] overall tuberculosis rates among children and adolescents are low and steadily declining, substantial heterogeneity exists in burden and trends across geographies and sociodemographic groups.” They further suggested that groups with the highest rates of tuberculosis could be prioritized to optimize the prognostic capacity of tuberculosis testing, as diagnostics currently have limited specificity and sensitivity. 

Reference

Cowger TL, Wortham JM,  Burton DC. Epidemiology of tuberculosis among children and adolescents in the USA, 2007-17: an analysis of national surveillance data [published online August 21, 2019]. Lancet Public Health. doi: 10.1016/S2468-2667(19)30134-3