March 24 is World TB Day. It was on this date in 1882 that physician Robert Koch announced the discovery of Mycobacterium tuberculosis, the causative agent of tuberculosis. Worldwide, activities are planned to raise awareness of TB and to support initiatives for prevention, better control, and ultimately the elimination of this disease.
Globally in 2015, the World Health Organization estimated there were 10.4 million new cases of TB, including 1 million in children. Data from the United States reveal that after 20 years of annual decline, the incidence of TB has plateaued. In 2015, 9,563 cases of TB disease were reported, including 440 cases in children less than 15 years of age. While the overall incidence was 3 cases per 100,000, the incidence among foreign-born persons was 15.1 cases per 100,000. There were 3,201 cases (33.5%) among U.S.-born individuals. Foreign-born persons accounted for 66.2% of cases; however, the majority of those cases were diagnosed several years after their arrival in the United States. The top five countries of origin of these individuals were China, India, Mexico, the Philippines, and Vietnam. In contrast, only one-quarter of all pediatric cases occurred in foreign-born children. Four states (California, Florida, New York, and Texas) reported more than 500 cases each in 2015, as they have for the last 7 consecutive years. In 2015, these states accounted for slightly more than half (4,839) of all cases (MMWR 2016 Mar 25;65[11]:273-8).
Dr. Bonnie M. Word
Why as pediatricians should we be concerned? TB in a child is a sentinel event and represents recent or ongoing transmission. Young children who are infected are more likely to progress to TB disease and develop severe manifestations such as miliary TB or meningitis. Children less than 4 years old and those with certain underlying disorders, including those with an immunodeficiency or who are receiving immunosuppressive agents, also are at greater risk for progression from infection to disease. Other predictors of disease progression include diagnosis of the infection within the past 2 years, use of chemotherapy and high-dose corticosteroids, as well as certain cancers, diabetes, and chronic renal failure.
Once infected, most children and adolescents remain asymptomatic. If disease occurs, symptoms develop 1-6 months after infection and include fever, cough, weight loss or failure to thrive, night sweats, and chills. Chest radiographic findings are nonspecific. Infiltrates and intrathoracic lymph node enlargement may or may not be present. However, our goal is to diagnose at-risk children with infection, treat them, and avoid their progression to TB disease.
Screening tests
The interferon-gamma release assay is a blood test that has a greater specificity than TST and requires only one visit. A positive test is seen in both latent TB infection and TB disease. There is no cross-reaction with BCG. This is the ideal test for prior BCG recipients and others who are unlikely to return for TST readings and are at least 5 years of age.
A chest radiograph is required to differentiate latent TB infection from TB disease. Latent TB infection is diagnosed when there is an absence of parenchymal disease, opacification, or intrathoracic adenopathy.
Treatment of latent TB infection versus TB disease is beyond the scope of this article. Consultation with an infectious disease expert is recommended.
For additional information and resources, go to www.cdc.gov/tb, and for a sample TB risk assessment tool, go to www.cdc.gov/tb/publications/ltbi/appendixa.htm.
As we mark the passing of another World TB Day, we have one goal – to identify, screen, and treat children and adolescents at risk for latent TB infection and help eliminate future cases of TB disease.
Dr. Word is a pediatric infectious disease specialist and director of the Houston Travel Medicine Clinic. She said she had no relevant financial disclosures.