Model estimates large global burden of childhood tuberculosis infection and potentially preventable future tuberculosis disease

Burden of childhood tuberculosis in 22 high-burden countries: a mathematical modelling study.

Dodd PJ, Gardiner E, Coghlan R, Seddon JA. Lancet Glob Health. 2014 Aug;2(8):e453-9. doi: 10.1016/S2214-109X(14)70245-1. Epub 2014 Jul 8.

Background: Confirmation of a diagnosis of tuberculosis in children (aged <15 years) is challenging; under-reporting can result even when children do present to health services. Direct incidence estimates are unavailable, and WHO estimates build on paediatric notifications, with adjustment for incomplete surveillance by the same factor as adult notifications. We aimed to estimate the incidence of infection and disease in children, the prevalence of infection, and household exposure in the 22 countries with a high burden of the disease.

Methods: Within a mechanistic mathematical model, we combined estimates of adult tuberculosis prevalence in 2010, with aspects of the natural history of paediatric tuberculosis. In a household model, we estimated household exposure and infection. We accounted for the effects of age, BCG vaccination, and HIV infection. Additionally, we tested sensitivity to key structural assumptions by repeating all analyses without variation in BCG efficacy by latitude.

Findings: The median number of children estimated to be sharing a household with an individual with infectious tuberculosis in 2010 was 15 319 701 (IQR 13 766 297-17 061 821). In 2010, the median number of Mycobacterium tuberculosis infections in children was 7 591 759 (5 800 053-9 969 780), and 650 977 children (424 871-983 118) developed disease. Cumulative exposure meant that the median number of children with latent infection in 2010 was 53 234 854 (41 111 669-68 959 804). The model suggests that 35% (23-54) of paediatric cases of tuberculosis in the 15 countries reporting notifications by age in 2010 were detected. India is predicted to account for 27% (22-33) of the total burden of paediatric tuberculosis in the 22 countries. The predicted proportion of tuberculosis burden in children for each country correlated with incidence, varying between 4% and 21%.

Interpretation: Our model has shown that the incidence of paediatric tuberculosis is higher than the number of notifications, particularly in young children. Estimates of current household exposure and cumulative infection suggest an enormous opportunity for preventive treatment.

Abstract  Full-text [free] access 

Editor’s notes: Estimating the burden of childhood tuberculosis has been largely neglected until recently. Children with tuberculosis rarely transmit and therefore from a control perspective, childhood tuberculosis does not notably contribute to the continuation of the tuberculosis epidemic. This modelling paper attempts to estimate the global burden of childhood tuberculosis infection and disease. Incidence estimates are made by using adult tuberculosis prevalence data to tackle the known limitations of using paediatric notification data. A second model estimates the prevalence of infection in children and household exposure, ignoring exposure outside of the household.  As with all mathematical model predictions, precision of estimates are dependent on the data used as inputs in the model. Despite these limitations, the paper draws attention to the fact that the burden of childhood tuberculosis infection and disease is significant and reflects failure of tuberculosis control in the 22 high-burden countries. The paper also highlights the fact that household contact tracing and preventive therapy in tuberculosis-exposed children could substantially reduce future tuberculosis-related morbidity.

Avoid TB deaths
Comorbidity, Epidemiology
Africa, Asia, Latin America
  • share