TB battle should cover latent infection in 1.7 billion people
Pete Dodd and Rein Houben
time to reevaluate the “one-third” figure, which has become an oral tradition.
In a new paper published in PLOS Medicine, we reconstructed the “force of infection” for TB – the chance that an individual would become infected with Mycobacterium tuberculosis – in 180 countries (equivalent to about 99% of the world’s population) over the past 80 years. We approached this by compiling data from surveys children already carry a latent TB infection testing for latent infection, largely prior to 1990. We found that closer to a quarter of today’s global population has a latent TB infection – around 1.7 billion people. More than 80% of this burden is concentrated in Asia and Africa, where it is usually concentrated in older age groups as the prevalence of infection increases with age. Despite this, we estimate that nearly 100m children (more than the entire population of Germany) already carry a latent TB infection.
We also worked out that even if all TB transmission stopped tomorrow, the current pool of 1.7 billion latent infections alone would prevent the number of those with TB from reaching the global targets set by the World Health Organisation for 2035, and the vision for TB elimination by 2050. It is clear that if we really want to make TB a disease of the past, we will need to address this pool of 1.7 billion. New diagnostic tools are needed accurately to identify those individuals with latent TB infections that are likely to progress to disease, and new tools are needed to safely treat them. Only then can the current guidelines for latent TB infection be expanded from their focus on relatively small high risk groups (for example recent close contacts of individuals with TB or those infected with HIV) to reach a wider population.
The sheer numbers of those infected show that TB is not only still with us, it also needs to become a priority if we are going to address this ancient disease that still infects over a billion people, including 100m children, and causes more than 10m cases of disease and nearly 2m deaths each year. It’s much more than a numbers game, TB is a deadly reality.
Pete Dodd is Research Associate in Health Economic Modelling, University of Sheffield. Rein Houben is Associate Professor in Infectious Disease Epidemiology, London School of Hygiene & Tropical Medicine