[Source Case Investigation Results for Children Under the Age of 5 Years with Tuberculosis in the Republic of Korea,...

Children with tuberculosis (TB) are highly likely to be infected by recent contact with a contagious patient with TB. When a patient with TB under the age of 5 is reported, an investigation is conducted to find the TB source. From 2016 to 2021, reports of patients with TB under the age of 5 reported according to the notice of diagnostic criteria for infectious diseases, case reports, and source case investigation results were retrospectively analyzed. A total of 88 patients with TB under the age of 5 were reported between 2016 and 2021. Of these, 25 (28.4%) were infected through household contacts. Twenty-six (29.5%) cases were infected with Mycobacterium bovis Bacillus Calmette-Guérin (BCG), a vaccine strain with BCG, after vaccination, and the source of the infection was not identified in 37 (42.0%) cases. Chest X-rays were performed on 107 household contacts of children with TB and 492 contacts in congregate settings such as daycare centers and kindergartens to find the source of infection of 37 pediatric patients with TB of unknown source; however, the source cases were not found. If a young child is diagnosed with TB, the possibility of recent exposure should be suspected, and finding the source is crucial to prevent further transmission in the community. M. bovis BCG infection is an adverse reaction caused by BCG vaccination; therefore, it is necessary to confirm these cases through genotype testing and exclude these from TB reporting to accurately understand the status of patients with TB under the age of 5.