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New evidence suggests a quarter of the world's population has latent tuberculosis

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  • New evidence suggests a quarter of the world's population has latent tuberculosis

    oct 26, 2016

    In rich countries, tuberculosis is sometimes thought of as a thing of the past, the disease that claimed Keats, Poe, Chopin.


    But globally, TB is today the number one infectious killer, causing an estimated 1.8m deathsin 2015.

    Unlike many bugs, infection with the bacterium that causes TB doesn’t usually result in disease.

    The usual dictum is that only 10% of people who are infected willever develop TB, but this may occur many years after initial infection.

    The flip side of this is that latent infection with Mycobacterium tuberculosis is far more common than the disease – and it is commonly stated that a third of all people worldwide carry it.

    However, the last systematic attempt to estimate the number of latent TB infections was 20 years ago. Since then, many things have changed. The world population has increased by over 20% and grown older; in China, the median age has increased by ten years over this period. At the same time, children make up nearly half of the population in most sub-Saharan countries in Africa.

    The fraction of people with TB disease has declined, despite upswings associated with HIV in some regions through the nineties. Developing new ways to address the pool of latent TB infection is now seen as an emerging front in its control. Clearly it’s 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.

    LINK TO FULL ARTICLE
    ?Addressing chronic disease is an issue of human rights ? that must be our call to arms"
    Richard Horton, Editor-in-Chief The Lancet

    ~~~~ Twitter:@GertvanderHoek ~~~ GertvanderHoek@gmail.com ~~~

  • #2
    The Global Burden of Latent Tuberculosis Infection: A Re-estimation Using Mathematical ModellingAbstract

    Background

    The existing estimate of the global burden of latent TB infection (LTBI) as “one-third” of the world population is nearly 20 y old. Given the importance of controlling LTBI as part of the End TB Strategy for eliminating TB by 2050, changes in demography and scientific understanding, and progress in TB control, it is important to re-assess the global burden of LTBI.

    Methods and Findings

    We constructed trends in annual risk in infection (ARI) for countries between 1934 and 2014 using a combination of direct estimates of ARI from LTBI surveys (131 surveys from 1950 to 2011) and indirect estimates of ARI calculated from World Health Organisation (WHO) estimates of smear positive TB prevalence from 1990 to 2014. Gaussian process regression was used to generate ARIs for country-years without data and to represent uncertainty. Estimated ARI time-series were applied to the demography in each country to calculate the number and proportions of individuals infected, recently infected (infected within 2 y), and recently infected with isoniazid (INH)-resistant strains. Resulting estimates were aggregated by WHO region. We estimated the contribution of existing infections to TB incidence in 2035 and 2050.

    In 2014, the global burden of LTBI was 23.0% (95% uncertainty interval [UI]: 20.4%–26.4%), amounting to approximately 1.7 billion people. WHO South-East Asia, Western-Pacific, and Africa regions had the highest prevalence and accounted for around 80% of those with LTBI. Prevalence of recent infection was 0.8% (95% UI: 0.7%–0.9%) of the global population, amounting to 55.5 (95% UI: 48.2–63.8) million individuals currently at high risk of TB disease, of which 10.9% (95% UI:10.2%–11.8%) was isoniazid-resistant. Current LTBI alone, assuming no additional infections from 2015 onwards, would be expected to generate TB incidences in the region of 16.5 per 100,000 per year in 2035 and 8.3 per 100,000 per year in 2050.

    Limitations included the quantity and methodological heterogeneity of direct ARI data, and limited evidence to inform on potential clearance of LTBI.

    Conclusions

    We estimate that approximately 1.7 billion individuals were latently infected with Mycobacterium tuberculosis (M.tb) globally in 2014, just under a quarter of the global population. Investment in new tools to improve diagnosis and treatment of those with LTBI at risk of progressing to disease is urgently needed to address this latent reservoir if the 2050 target of eliminating TB is to be reached.





    In this mathematical modelling study, Rein Houben and colleagues provide updated estimates of latent tuberculosis infection worldwide and its implications of this reservoir with respect to goals for eliminating tuberculosis.
    ?Addressing chronic disease is an issue of human rights ? that must be our call to arms"
    Richard Horton, Editor-in-Chief The Lancet

    ~~~~ Twitter:@GertvanderHoek ~~~ GertvanderHoek@gmail.com ~~~

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