Modelling the effect of a nutritional shock on tuberculosis in India

Environmental or social changes and shocks that reduce access to adequate nutrition have potential consequences for tuberculosis (TB), as undernutrition is a major driver of TB incidence and poor TB treatment outcomes.

We developed a transmission model of TB in India with an explicit body mass index (BMI) strata linked to disease progression and treatment outcomes, calibrated to country-specific TB estimates. We projected nutritional shock scenarios affecting supply chains, similar to those experienced at the beginning of the war in Ukraine, using the LandSyMM food system model, compared to a continuation of previous food system trends. Within each scenario, increases in food, fertiliser, and energy prices were linked to changes in the population BMI distribution by food availability and prices. We estimated the impact on TB incidence and mortality in India between 2022 and 2035 of these nutritional shock scenarios compared to maintenance of prior trends.

The worst-case scenario, involving sustained increases in food, fertiliser, and energy prices, predicted that shocks increasing undernutrition could result in a 5.0% (95% uncertainty interval = 4.4, 5.9) and 4.9% (4.2, 5.9) increase in TB incidence and mortality respectively in India in 2035 compared to continuation of previous food system trends. In this scenario, an additional 1.1 million (0.9, 1.3) TB episodes and 177.5 thousand (144.7, 224.3) TB deaths were predicted to occur between 2022 and 2035.

Shocks affecting the population-level BMI distribution could lead to changes in the burden of TB disease. Our findings suggest that the impact of crises on TB disease may be underestimated if the impacts of external shocks on nutrition are not explicitly considered.