Tuberculosis Transmission in Danish Children: A Nationwide Register-based Study

BACKGROUND: Tuberculosis (TB) remains a major public health issue among children worldwide. Data on TB transmission in children living in low-incidence countries is limited. METHODS: We studied TB transmission in ethnic Danish children younger than 15 years of age between 2000 and 2013. Identification of children with TB disease and information on demographics and TB contacts were retrieved from the national TB surveillance register and the International Reference Laboratory of Mycobacteriology. RESULTS: In total, 88 children with TB disease were identified in the study period, corresponding to a mean annual incidence of 6.9 per 1,000,000 children younger than 15 years of age. The male to female ratio was 1.3. Median age was 5 years (interquartile range, 3-8.5). Seventy-three (83%) children had a known TB contact of which 60% was among household contacts with recent TB, predominantly parents. Sixty-six (75%) children were classified as part of epidemiologic clusters. Thirty-five (40%) children had culture verified TB of which information on genotypes was available for 34 (97%). Of these, 35% belonged to cluster C2/1112-15, the most prevalent cluster among adult Danes. CONCLUSIONS: We found on-going TB transmission in Danish children within the households of a low TB incidence population. These findings emphasize the need for early diagnosis of TB in children, thorough contact tracing and increased focus on risk groups.