A number of factors are contributing to the spread of active TB among children and adults alike. Despite broad progress in the last few decades, the emergence of MDR-TB and continued prevalence of HIV, have combined with social and lifestyle factors such as smoking, diabetes and accelerating urbanisation, to threaten a renewed epidemic. Due to their special status as dependents, these trends affect children both directly and indirectly, via adult caregivers.
Co-infection with HIV and TB remains the biggest driver of mortality among people with HIV of all ages, with TB accounting for 39 percent of AIDS-related deaths in 2015.30 Currently there are approximately 3.4 million children living with HIV and 14 million individuals, of all ages, co-infected with HIV and TB, most in the developing world.31,32 Foetuses and newborns are susceptible to maternal transmission of both diseases, while children orphaned by AIDS or TB are challenged in seeking medical attention and adhering to drug regimens.33,34 WHO estimates there are 16.5 million children orphaned by the loss of one or both parents to HIV and 9.7 million orphaned by TB.3536,
Tobacco consumption is strongly correlated with development of active TB, accounting for over a fifth of global TB incidence, as well as recurrence.37,38,39 Currently, 1.1 billion people around the world smoke tobacco, up from 721 million in 1980, with most of this increase in the developing world. Around 40 percent of children are exposed to second-hand smoke at home and 6.6 percent of African children are smokers themselves, as are some 625,000 Indian children aged 10-14 years.40,41,42 Globally, WHO estimates that between 80,000 and 100,000 children become smokers every day, most of them living in Asia.43
Type 2 diabetes increases the risk of developing active TB threefold, as well as raising the risk of relapse.44,45 Global prevalence of type 2 diabetes almost doubled from 4.7 percent in 1980 to 8.5 percent in 2014, due in large part to changing diets and increasingly sedentary lifestyles in the developing world.46 The number of children diagnosed with type 2 diabetes has also increased, representing almost half of all new diabetes diagnoses among children.47
Finally, rapid urbanisation is also contributing to the spread of TB. The proportion of the world’s population living in urban areas increased from 40 percent in 1980 to 54 percent in 2015, and a further increase of two-thirds is expected by 2050.48 The trend is led by the developing world49 where unlicensed building remains common due to weakness in state authority.50,51 In many cases, unregulated habitations lack adequate ventilation and sanitation, providing breeding grounds for TB, which spreads from person to person through the air.52,53 The numbers of people living in slums will more than double to three billion by 205054 – a special concern as most children with TB contract the disease from family members in a household setting.55