In a recent study published in The Lancet Infectious Diseases, researchers assessed the global, national, and regional burden and trends in tuberculosis.

Study: Global, regional, and national age-specific progress towards the 2020 milestones of the WHO End TB Strategy: a systematic analysis for the Global Burden of Disease Study 2021. Image Credit: SewCreamStudio/Shutterstock.com

Background

Tuberculosis is a significant contributor to the global disease burden despite being a preventable and curable disease. It accounts for over a million deaths each year, and in 2019, it was the leading cause of death due to a single infectious agent. Global initiatives to address tuberculosis have been prominent since the 1990s.

The World Health Organization (WHO) End TB Strategy aims to accelerate progress by reducing tuberculosis incidence and deaths by 90% and 95% between 2015 and 2035.

Therefore, evaluations of the trends in the global tuberculosis burden are necessary to assess progress in achieving these targets.

About the study

In the present study, researchers examined the levels and trends in global tuberculosis burden and age-specific achievement of incidence and mortality milestones. They used data from the Global Burden of Diseases, Injuries, and Risk Factors Study 2021.

The team included data on vital registration, mortality surveillance, and minimally invasive tissue sample diagnoses for tuberculosis mortality in those without human immunodeficiency virus (HIV) coinfection.

The cause-of-death ensemble modeling generated mortality estimates in those without HIV coinfection by age, sex, location, and year. Further, a population-attributable fraction approach was used to estimate age-specific deaths among those with HIV.

In parallel, age-specific tuberculosis prevalence, incidence, and mortality were modeled using disease-model Bayesian meta-regression. Tuberculosis deaths attributable to risk factors were computed.

Further, the impact of the coronavirus disease 2019 (COVID-19) pandemic on mortality was evaluated for countries with at least 10 tuberculosis deaths in 2019 for each age group.

Tuberculosis incidence and mortality estimates were aggregated by HIV status, and all-form tuberculosis burden estimates were presented for five age groups – < 5, 5–14, 15–49, 50–69, and ≥ 70 years. Incidence- and mortality-specific annualized rates of change (ARCs) were reported.

Findings

Overall, 9.4 and 1.35 million tuberculosis cases and deaths occurred in 2021, respectively. Of these, tuberculosis and HIV coinfection cases accounted for a million cases and 205,000 deaths. The age-standardized incidence and mortality rates were 115 and 16.2 per 100,000 population, respectively. These rates declined by 37% and 61.1% between 1990 and 2021.

In 2021, 3.8% of incident cases and 4.5% of deaths were reported in those under five years, and 4.7% of cases and 1.5% of deaths occurred in the 5–14 age group. Most cases (54.9%) and deaths (36.4%) in 2021 occurred in the 15–49 age group.

In 2021, incidence rates exceeded 100 per 100,000 individuals in those aged five or younger across 34 countries and 5–14 across 14 countries.

Further, incidence rates surpassed 500 per 100,000 individuals in the 15–49, 50–69, and ≥ 70 age groups in nine, 33, and 50 countries, respectively.

Mortality rates were greater than 25 per 100,000 individuals in the < 5, 5–14, and 15–49 age groups in 20, 1, and 37 countries, respectively. Notably, mortality rates exceeding 300 per 100,000 individuals were observed in the 50–69 and ≥ 70 age groups in eight and 44 countries, respectively.

ARCs in tuberculosis incidence were the largest in those aged <5 and 5–14 between 2020 and 2021, reducing by 4.1% and 3.7%, respectively, whereas reductions in adult age groups were around 2%.

Moreover, the largest ARCs for mortality rates were observed in the same age groups. Central Asia and Central and Eastern Europe had the largest age-standardized ARCs between 2010 and 2021.

Globally, all-age incidence rates reduced by 6.26% between 2015 and 2020, with a 4.9% decline in males and 7.9% in females. In the same period, global deaths due to tuberculosis declined by 11.9%, with a greater change in females (13.8%). Global tuberculosis deaths decreased to one million after removing the cumulative effects of risk factors (diabetes, smoking, and alcohol use).

Forty-one countries were included in the analysis of the impact of COVID-19. Accordingly, 50,900 deaths due to tuberculosis were expected in 2020 compared to 45,500 deaths observed, corresponding to 5,340 fewer deaths than expected.

Twenty countries continued to report data through 2021. In these countries, 39,600 deaths were expected compared to 39,000 observed.

Conclusions

The first WHO End TB interim milestones were not achieved in 2020, with only 6% and 12% reductions in incidence and mortality rates between 2015 and 2020, respectively.

There was differential progress across age groups; people under 15 showed the sharpest decreases, whereas the older groups had minimal declines.

The End TB incidence and mortality milestones were reached in 2020 by only 15 and 17 countries, respectively.

As such, control programs should evaluate these countries to explore the drivers of their progress. Moreover, the impact of the COVID-19 pandemic was heterogeneous and uncertain, warranting additional data.