Estimating Long-term Tuberculosis Reactivation Rates in Australian Migrants

The Impact of Preventive Treatment for Multidrug- and Rifampin-Resistant Tuberculosis Exceeds Trial-Based Estimates

BACKGROUND

Several clinical trials of tuberculosis preventive treatment (TPT) for household contacts of patients with multidrug- or rifampin-resistant tuberculosis (MDR/RR-TB) are nearing completion. The potential benefits of delivering TPT to MDR/RR-TB contacts extend beyond the outcomes that clinical trials can measure.

METHODS

We developed an agent-based, household-structured TB and MDR/RR-TB transmission model, calibrated to an illustrative setting in India. We simulated contact investigation in households of patients with MDR/RR-TB, comparing an MDR/RR-TPT regimen (assuming 6-month duration, 70% efficacy) and associated active case finding against alternatives of contact investigation without TPT or no household intervention. We simulated the TB and MDR/RR-TB incidence averted relative to placebo over 2 years, as measurable by a typical trial, as well as the incidence averted over a longer time horizon, in the broader population, and relative to no contact investigation.

RESULTS

Observing TPT and placebo recipients for 2 years as in a typical trial, MDR/RR-TPT was measured to prevent 72% (interquartile range, 45%-100%) of incident MDR/RR-TB among recipients; the median number needed to treat (NNT) to prevent 1 MDR/RR-TB case was 73, compared to placebo. This NNT decreased to 54 with 13-18 years of observation, to 27 when downstream transmission effects were also considered, and to 12 when the effects of active TB screening were included by comparing to a no-household-contact-intervention scenario.

CONCLUSIONS

If forthcoming trial results demonstrate efficacy, the long-term population impact of TPT for MDR/RR-TB-including the large effect of increased active TB detection among MDR/RR-TB contacts-could be much greater than suggested by trial outcomes alone.

How We Treat Drug-Susceptible Pulmonary Tuberculosis: A Practical Guide for Clinicians

Tuberculosis (TB) remains one of the leading causes of morbidity and mortality worldwide and pulmonary TB (PTB) is the main variant responsible for fueling transmission of the infection. Effective treatment of drug-susceptible (DS) TB is crucial to avoid the emergence of Mycobacterium tuberculosis-resistant strains. In this narrative review, through a fictional suggestive case of DS PTB, we guide the reader in a step-by-step commentary to provide an updated review of current evidence in the management of TB, from diagnosis to post-treatment follow-up. World Health Organization and Centre for Diseases Control (CDC) guidelines for TB, as well as the updated literature, were used to support this manuscript.

Tuberculosis incidence in foreign-born people residing in European countries in 2020

BackgroundEuropean-specific policies for tuberculosis (TB) elimination require identification of key populations that benefit from TB screening.AimWe aimed to identify groups of foreign-born individuals residing in European countries that benefit most from targeted TB prevention screening.MethodsThe Tuberculosis Network European Trials group collected, by cross-sectional survey, numbers of foreign-born TB patients residing in European Union (EU) countries, Iceland, Norway, Switzerland and the United Kingdom (UK) in 2020 from the 10 highest ranked countries of origin in terms of TB cases in each country of residence. Tuberculosis incidence rates (IRs) in countries of residence were compared with countries of origin.ResultsData on 9,116 foreign-born TB patients in 30 countries of residence were collected. Main countries of origin were Eritrea, India, Pakistan, Morocco, Romania and Somalia. Tuberculosis IRs were highest in patients of Eritrean and Somali origin in Greece and Malta (both > 1,000/100,000) and lowest among Ukrainian patients in Poland (3.6/100,000). They were mainly lower in countries of residence than countries of origin. However, IRs among Eritreans and Somalis in Greece and Malta were five times higher than in Eritrea and Somalia. Similarly, IRs among Eritreans in Germany, the Netherlands and the UK were four times higher than in Eritrea.ConclusionsCountry of origin TB IR is an insufficient indicator when targeting foreign-born populations for active case finding or TB prevention policies in the countries covered here. Elimination strategies should be informed by regularly collected country-specific data to address rapidly changing epidemiology and associated risks.

Trials underestimate the impact of preventive treatment for household contacts exposed to multidrug-resistant tuberculosis: a simulation study

Background

Several clinical trials of tuberculosis preventive treatment (TPT) for household contacts of patients with multidrug-resistant tuberculosis (MDR-TB) are nearing completion. The potential benefits of TPT for MDR-TB contacts extend beyond the outcomes that clinical trials can measure.

Methods

We developed an agent-based, household-structured TB and MDR-TB transmission model, calibrated to an illustrative setting in India, the country accounting for 26% of global MDR-TB burden. We simulated household contact investigation for contacts of patients with MDR-TB, comparing an MDR-TPT regimen against alternatives of isoniazid preventive treatment, household contact investigation without TPT, or no household contact intervention. We simulated outcomes of a clinical trial and estimated the patient-level and population-level effects over a longer time horizon.

Findings

During two years of follow-up per recipient, a simulated 6-month MDR-TPT regimen with 70% efficacy against both DS- and MDR-TB infection could prevent 72% [Interquartile range (IQR): 45 - 100%] of incident MDR-TB among TPT recipients (number needed to treat (NNT) 73 [44 - 176] to prevent one MDR-TB case), compared to household contact investigation without TPT. This NNT decreased to 54 [30 - 183] when median follow-up was increased from two to 16 years, to 27 [11 - Inf] when downstream transmission effects were also considered, and to 12 [8 - 22] when these effects were compared to a scenario of no household contact intervention.

Interpretation

If forthcoming trial results demonstrate efficacy, the long-term population impact of MDR-TPT implementation could be much greater than suggested by trial outcomes alone.

Funding

NIH K01AI138853 and K08AI127908; Johns Hopkins Catalyst Award.

Tuberculosis notifications in regional Victoria, Australia: Implications for public health care in a low incidence setting

BACKGROUND

Regionality is often a significant factor in tuberculosis (TB) management and outcomes worldwide. A wide range of context-specific factors may influence these differences and change over time. We compared TB treatment in regional and metropolitan areas, considering demographic and temporal trends affecting TB diagnosis and outcomes.

METHODS

Retrospective analyses of data for patients notified with TB in Victoria, Australia, were conducted. The study outcomes were treatment delays and treatment outcomes. Multivariable Cox proportional hazard model analyses were performed to investigate the effect of regionality in the management of TB. Six hundred and eleven (7%) TB patients were notified in regional and 8,163 (93%) in metropolitan areas between 1995 and 2019. Of the 611 cases in the regional cohort, 401 (66%) were overseas-born. Fifty-one percent of the overseas-born patients in regional Victoria developed TB disease within five years of arrival in Australia. Four cases of multidrug-resistant tuberculosis were reported in regional areas, compared to 97 cases in metropolitan areas. A total of 3,238 patients notified from 2012 to 2019 were included in the survival analysis. The time follow-up for patient delay started at symptom onset date, and the event was the presentation to the healthcare centre. For healthcare system delay, follow-up time began at the presentation to the healthcare centre, and the event was commenced on TB treatment. Cases with extrapulmonary TB in regional areas have a non-significantly longer healthcare system delay than patients in metropolitan (median 64 days versus 54 days, AHR = 0.8, 95% CI 0.6-1.0, P = 0.094).

CONCLUSION

Tuberculosis in regional Victoria is common among the overseas-born population, and patients with extrapulmonary TB in regional areas experienced a non-significant minor delay in treatment commencement with no apparent detriment to treatment outcomes. Improving access to LTBI management in regional areas may reduce the burden of TB.

Whole genome sequencing for tuberculosis in Victoria, Australia: A genomic implementation study from 2017 to 2020

Background

Whole genome sequencing (WGS) is increasingly used by tuberculosis (TB) programs to monitor Mycobacterium tuberculosis (Mtb) transmission. We aimed to characterise the molecular epidemiology of TB and Mtb transmission in the low-incidence setting of Victoria, Australia, and assess the utility of WGS.

Methods

WGS was performed on all first Mtb isolates from TB cases from 2017 to 2020. Potential clusters (≤12 single nucleotide polymorphisms [SNPs]) were investigated for epidemiological links. Transmission events in highly-related (≤5 SNPs) clusters were classified as likely or possible, based on the presence or absence of an epidemiological link, respectively. Case characteristics and transmission settings (as defined by case relationship) were summarised. Poisson regression was used to examine associations with secondary case number.

Findings

Of 1844 TB cases, 1276 (69.2%) had sequenced isolates, with 182 (14.2%) in 54 highly-related clusters, 2-40 cases in size. Following investigation, 140 cases (11.0% of sequenced) were classified as resulting from likely/possible local-transmission, including 82 (6.4%) for which transmission was likely. Common identified transmission settings were social/religious (26.4%), household (22.9%) and family living in different households (7.1%), but many were uncertain (41.4%). While household transmission featured in many clusters (n = 24), clusters were generally smaller (median = 3 cases) than the fewer that included transmission in social/religious settings (n = 12, median = 7.5 cases). Sputum-smear-positivity was associated with higher secondary case numbers.

Interpretation

WGS results suggest Mtb transmission commonly occurs outside the household in our low-incidence setting. Further work is required to optimise the use of WGS in public health management of TB.

Funding

The Victorian Tuberculosis Program receives block funding for activities including case management and contact tracing from the Victorian Department of Health. No specific funding for this report was received by manuscript authors or the Victorian Tuberculosis Program, and the funders had no role in the study design, data collection, data analysis, interpretation or report writing.

Detecting Mycobacterium tuberculosis Infection in Children Migrating to Australia

In 2015, Australia updated premigration screening for tuberculosis (TB) disease in children 2-10 years of age to include testing for infection with Mycobacterium tuberculosis and enable detection of latent TB infection (LTBI). We analyzed TB screening results in children <15 years of age during November 2015-June 2017. We found 45,060 child applicants were tested with interferon-gamma release assay (IGRA) (57.7% of tests) or tuberculin skin test (TST) (42.3% of tests). A total of 21 cases of TB were diagnosed: 4 without IGRA or TST, 10 with positive IGRA or TST, and 7 with negative results. LTBI was detected in 3.3% (1,473/44,709) of children, for 30 applicants screened per LTBI case detected. LTBI-associated factors included increasing age, TB contact, origin from a higher TB prevalence region, and testing by TST. Detection of TB and LTBI benefit children, but the updated screening program's effect on TB in Australia is likely to be limited.

Case Report: Tuberculosis Autoregression after Minimal Treatment and Review of the Literature

Mycobacterium tuberculosis (Mtb) is a complex pathogen causing multiple possible disease states in its host including latency, active disease, and elimination. While there is reasonable indirect evidence of elimination of tuberculosis (TB) in the absence of treatment, direct reports of autoregression are rare. We report a case of smear-negative, polymerase chain reaction (PCR)-positive TB disease regression in the absence of therapy due to severe adverse effects from antimycobacterial drugs. Indirect reports of TB autoregression, or self-cure, in the literature are reviewed, and an updated framework for conceptualizing Mtb infection is discussed.

Demographic Control Measure Implications of Tuberculosis Infection for Migrant Workers across Taiwan Regions

A sharp increase in migrant workers has raised concerns for TB epidemics, yet optimal TB control strategies remain unclear in Taiwan regions. This study assessed intervention efforts on reducing tuberculosis (TB) infection among migrant workers. We performed large-scale data analyses and used them to develop a control-based migrant worker-associated susceptible-latently infected-infectious-recovered (SLTR) model. We used the SLTR model to assess potential intervention strategies such as social distancing, early screening, and directly observed treatment, short-course (DOTS) for TB transmission among migrant workers and locals in three major hotspot cities from 2018 to 2023. We showed that social distancing was the best single strategy, while the best dual measure was social distancing coupled with early screening. However, the effectiveness of the triple strategy was marginally (1-3%) better than that of the dual measure. Our study provides a mechanistic framework to facilitate understanding of TB transmission dynamics between locals and migrant workers and to recommend better prevention strategies in anticipation of achieving WHO's milestones by the next decade. Our work has implications for migrant worker-associated TB infection prevention on a global scale and provides a knowledge base for exploring how outcomes can be best implemented by alternative control measure approaches.

Are we underestimating the annual risk of infection with Mycobacterium tuberculosis in high-burden settings?

The annual risk of infection with Mycobacterium tuberculosis determines a population's exposure level and thus the fraction of incident tuberculosis resulting from recent infection (often considered as having occurred within the past 2 years). Contemporary annual risk of infection estimates centre around 1% in most high-burden countries. We present three arguments why these estimates-primarily derived from cross-sectional tuberculin surveys in young school children (aged 5-12 years)-might underrepresent the true annual risk of infection. First, young children are expected to have lower risk of infection than older adolescents and adults (ie, those aged 15 years and older). Second, exposure might not lead to a positive test result in some individuals. Third, cross-sectional surveys might overlook transient immune responses. Accounting for these biases, the true annual risk of infection among adults in high-burden settings is probably closer to 5-10%. Consequently, most tuberculosis in those settings should reflect infection within the past 2 years rather than remote infection occurring many years ago. Under this reframing, major reductions in tuberculosis incidence could be achievable by focusing on the minority of people who have been recently infected.

TB, focussed tools, and the right schools: estimated impact and cost of a targeted student screening program for tuberculosis infection

BACKGROUND

The WHO recommends targeted screening for latent tuberculosis infection (LTBI) amongst high-risk populations. Recent studies that evaluate targeted school- based programmes in low burden settings are scarce.

AIMS

To evaluate a school screening programme for recently arrived migrant students from moderate and high tuberculosis (TB) burden countries and estimate 1- the number of cases of active TB that were prevented and 2- the cost per case of active TB prevented.

METHODS

Students were screened with tuberculin skin tests (TST) at schools with a high migrant population intake. Those with positive results were referred for specialist evaluation. Outcomes were retrospectively assessed using five years of prospectively collected data. Cost data were collected. Main outcomes measured were the number of children were diagnosed with LTBI who completed treatment, and programme costs.

RESULTS

Of 4728 student screened, 295(6.2%) were diagnosed with LTBI. Of these, 273 (92.5%) were offered preventive therapy, 242 (82.0%) commenced and 204 (69.2%) completed therapy. The number needed to screen (NNS) was 23 per completed course of preventive treatment for LTBI. Assuming a 10% lifetime risk of reactivation, the NNS was 386 per case of TB disease notification avoided. The cost of screening was $23 932 AUD per case of TB disease avoided.

CONCLUSIONS

This TB strategy is supported by the high rate of TB infection in the student group, the treatment uptake and completion rates. Cost-benefit is linked with lifetime risk of TB reactivation. Targeted school screening programmes represent an important opportunity for TB control in low-burden settings. This article is protected by copyright. All rights reserved.

Modeling the Cost-Effectiveness of Latent Tuberculosis Screening and Treatment Strategies in Recent Migrants to a Low-Incidence Setting

Many tuberculosis (TB) cases in low-incidence settings are attributed to reactivation of latent TB infection (LTBI) acquired overseas. We assessed the cost-effectiveness of community-based LTBI screening and treatment strategies in recent migrants to a low-incidence setting (Australia). A decision-analytical Markov model was developed that cycled 1 migrant cohort (≥11-year-olds) annually over a lifetime from 2020. Postmigration/onshore and offshore (screening during visa application) strategies were compared with existing policy (chest x-ray during visa application). Outcomes included TB cases averted and discounted cost per quality-adjusted life-year (QALY) gained from a health-sector perspective. Most recent migrants are young adults and cost-effectiveness is limited by their relatively low LTBI prevalence, low TB mortality risks, and high emigration probability. Onshore strategies cost at least $203,188 (Australian) per QALY gained, preventing approximately 2.3%-7.0% of TB cases in the cohort. Offshore strategies (screening costs incurred by migrants) cost at least $13,907 per QALY gained, preventing 5.5%-16.9% of cases. Findings were most sensitive to the LTBI treatment quality-of-life decrement (further to severe adverse events); with a minimal decrement, all strategies caused more ill health than they prevented. Additional LTBI strategies in recent migrants could only marginally contribute to TB elimination and are unlikely to be cost-effective unless screening costs are borne by migrants and potential LTBI treatment quality-of-life decrements are ignored.

Tuberculosis trend among native and foreign-born people over a 17 year period (2004-2020) in a large province in Northern Italy

Tuberculosis (TB) incidence should decline by 20% in the Europe in 2015–2020, in line with End-TB milestones. We retrospectively evaluated TB notifications in the province of Brescia from 2004 to 2020. Cases were classified per patient origin and entitlement to Health Assistance for foreign born people: Italians (ITA), Foreigners permanently entitled (PEF) or Temporarily Entitled (TEF) to Health Regional Assistance. Poisson regression analysis was performed to assess associations between incidence and age, sex, continent of origin and year of notification. Overall 2279 TB cases were notified: 1290 (56.6%) in PEF, 700 (30.7%) in ITA and 289 (12.7%) in TEF. Notifications declined from 15.2/100,000 in 2004 to 6.9/100,000 in 2020 (54.6% reduction, temporary increase in 2013–2018 for TEF). Age (Incidence Risk Ratio, IRR, 1.02, 1.019–1.024 95%CI), sex (IRR 1.22, 1.12–1.34 95%CI), and continent of origin were positively associated with notifications (IRR 34.8, 30.8–39.2 95%CI for Asiatic, and IRR 20.6, 18.1–23.4 95%CI for African origin), p < 0.001. Notification decline was sharper in 2020, especially among TEF. End-TB milestone for 2020 was reached, but foreigners continue to represent a high risk group for the disease. Discontinuation of services due to the COVID-19 pandemic was associated with a sharp decrease in TB notification in 2020.

Self-clearance of Mycobacterium tuberculosis infection: implications for lifetime risk and population at-risk of tuberculosis disease

Background: it is widely assumed that individuals with Mycobacterium tuberculosis (Mtb) infection remain at lifelong risk of tuberculosis (TB) disease. However, there is substantial evidence that self-clearance of Mtb infection can occur. We infer a curve of self-clearance by time since infection and explore its implications for TB epidemiology. Methods and findings: data for self-clearance were inferred using post-mortem and tuberculin-skin-test reversion studies. A cohort model allowing for self-clearance was fitted in a Bayesian framework before estimating the lifetime risk of TB disease and the population infected with Mtb in India, China and Japan in 2019. We estimated that 24.4% (17.8-32.6%, 95% uncertainty interval (UI)) of individuals self-clear within 10 years of infection, and 73.1% (64.6-81.7%) over a lifetime. The lifetime risk of TB disease was 17.0% (10.9-22.5%), compared to 12.6% (10.1-15.0%) assuming lifelong infection. The population at risk of TB disease in India, China and Japan was 35-80% (95% UI) smaller in the self-clearance scenario. Conclusions: the population with a viable Mtb infection may be markedly smaller than generally assumed, with such individuals at greater risk of TB disease. The ability to identify these individuals could dramatically improve the targeting of preventive programmes and inform TB vaccine development, bringing TB elimination within reach of feasibility.

Perspectives of Vietnamese, Sudanese and South Sudanese immigrants on targeting migrant communities for latent tuberculosis screening and treatment in low-incidence settings: A report on two Victorian community panels

BACKGROUND

Tuberculosis (TB) elimination strategies in Australia require a focus on groups who are at highest risk of TB infection, such as immigrants from high-burden settings. Understanding attitudes to different strategies for latent TB infection (LTBI) screening and treatment is an important element of justifiable elimination strategies.

METHOD

Two community panels were conducted in Melbourne with members of the Vietnamese (n = 11), Sudanese and South Sudanese communities (n = 9). Panellists were provided with expert information about LTBI and different screening and health communication strategies, then deliberated on how best to pursue TB elimination in Australia.

FINDINGS

Both panels unanimously preferred LTBI screening to occur pre-migration rather than in Australia. Participants were concerned that post-migration screening would reach fewer migrants, noted that conducting LTBI screening in Australia could stigmatize participants and that poor awareness of LTBI would hamper participation. If targeted screening was to occur in Australia, the Vietnamese panel preferred 'place-based' communication strategies, whereas the Sudanese and South Sudanese panel emphasized that community leaders should lead communication strategies to minimize stigma. Both groups emphasized the importance of maintaining community trust in Australian health service providers, and the need to ensure targeting did not undermine this trust.

CONCLUSION

Pre-migration screening was preferred. If post-migration screening is necessary, the potential for stigma should be reduced, benefit and risk profile clearly explained and culturally appropriate communication strategies employed. Cultural attitudes to health providers, personal health management and broader social vulnerabilities of targeted groups need to be considered in the design of screening programs.

Tuberculosis in migrants - screening, surveillance and ethics

Tuberculosis (TB) is the leading infectious cause of human mortality and is responsible for nearly 2 million deaths every year. It is often regarded as a 'silent killer' because it predominantly affects the poor and marginalized, and disease outbreaks occur in 'slow motion' compared to Ebola or coronavirus 2 (COVID-19). In low incidence countries, TB is predominantly an imported disease and TB control in migrants is pivotal for countries to progress towards TB elimination in accordance with the World Health Organisations (WHO's) End TB strategy. This review provides a brief overview of the different screening approaches and surveillance processes that are in place in low TB incidence countries. It also includes a detailed discussion of the ethical issues related to TB screening of migrants in these settings and the different interests that need to be balanced. Given recognition that a holistic approach that recognizes and respects basic human rights is required to end TB, the review considers the complexities that require consideration in low-incidence countries that are aiming for TB elimination.

Insights into culturally appropriate latent tuberculosis infection (LTBI) screening in NSW: perspectives of Indian and Pakistani migrants

OBJECTIVE

Latent tuberculosis (LTBI) case-finding and treatment are a focus of TB elimination in Australia. We sought the perspectives of migrants from two high-burden countries likely to be targeted by this strategy.

METHODS

To understand perceptions of migrant groups in Australia on LTBI screening, 28 in-depth interviews were conducted with Indian and Pakistani community members recruited purposively through local organisations in the Illawarra region, New South Wales. Drawing on local TB policy, data collected qualitatively was analysed using framework methodologies.

RESULTS

Australia's immigration system prioritises migrants of higher socioeconomic status. Participants supported elimination but perceived TB as a disease of the poor and not relevant to them. Lack of understanding of LTBI and sensitivity to being 'targeted' are further barriers to screening participation.

CONCLUSION

Information provision and targeting rationale are an essential preamble to LTBI screening. Migration appears to modify cultural attitudes to TB, but not significantly. Despite less stigma surrounding TB in Australian contexts, testing privacy and confidentiality, and limiting public identification of specific groups remain important to program acceptability. Implications for public health: Progress towards TB elimination can be enhanced by consulting with targeted communities, using existing networks for communication and service provision; emphasising prevention benefits.