Background Approximately 96% of rifampicin resistance/multidrug-resistant tuberculosis (RR/MDR-TB) cases in Rwanda result from direct transmission rather than acquired resistance. However, the nationwide spatial distribution and transmission dynamics of RR/MDR-TB remain poorly characterised. This study aims to analyse spatial patterns of RR/MDR-TB in Rwanda and explore relationships between spatial proximity and RR/MDR-TB strains’ genetic relatedness.Methods We conducted a retrospective analysis of 249 confirmed RR-TB cases across Rwanda from 2017 to 2024, using the known geolocations of patients’ residences. Spatial and space-time clustering was assessed using Kulldorff’s scan statistics. Demographic and socioeconomic determinants were evaluated using multivariable regression. For 201 cases with whole-genome sequencing data, we performed transmission analysis using a 5-SNP threshold to define recent transmission clusters and investigated spatial relationships within genetically related strains.Results Significant spatial clustering of RR/MDR-TB was identified in 21 sectors, mainly in Nyarugenge, southern Gasabo and western Kicukiro (relative risk: 10.06; p<0.001). Our multivariable analysis showed that population density is positively associated with case notification rates. Molecular analysis revealed 88.5% of cases belonged to genotype clusters defined using a 12-SNP threshold, with 73.6% forming clusters at a strict 5-SNP threshold. Spatial K-function analysis of the six major clusters revealed heterogeneous transmission patterns, characterised by both tightly clustered outbreaks and regional transmission networks that spanned administrative boundaries. Most clusters (5/6) extended beyond Kigali, indicating that transmission networks operate across administrative divides.Conclusion RR/MDR-TB in Rwanda shows significant spatial clustering with transmission occurring through both localised and regional networks. Integrating genomic and spatial data reveals transmission patterns that extend beyond household contacts and administrative boundaries. These findings underscore the need to implement geographically targeted interventions that address community-level transmission to control RR/MDR-TB in Rwanda effectively.

BACKGROUND:The Xpert assay has revolutionized the rapid detection of resistance to rifampicin. However, Xpert has its pitfalls. We explored potential determinants of false-positive rifampicin resistance when using Xpert, aiming to refine the precision of tuberculosis diagnostics and subsequently contribute to better patient outcomes. METHODS:This is a retrospective cross-sectional analysis of archived Xpert files from the South Kivu province, used to diagnose Mycobacterium tuberculosis (MTB) between 2013 and 2018. Xpert cycle threshold was extracted for each molecular beacon probe, and ΔCt was calculated. We used the MTBDRplus line-probe assay, which covers the same 81-bp RRDR, as a reference test. RESULTS:Of 1900 samples positive for MTB, 220 (11.2%) were rifampicin resistant. Of the 141 patients' sputum samples that had results for both Xpert and MTBDRplus, 45 (31.9%) showed discordant results with Xpert, indicating rifampicin resistance while MTBDRplus indicated rifampicin susceptibility, suggesting false-positive rifampicin resistance detection by Xpert, predominantly in samples with very low (Ct > 28, odds ratio [OR] = 2.23, 95% CI: 1.30-3.82) or low (Ct 22-28, OR = 1.81, 95% CI: 1.21-2.71) bacterial loads. Probe E was the most frequently missed probe, followed by multiple probe dropouts or absence of probe binding (OR = 1.5, 95% CI: .731-3.076). CONCLUSIONS:Our findings indicate that low and very low MTB bacterial loads in sputum are strongly associated with discordant rifampicin resistance results when using Xpert. Further research into underlying mechanisms is needed to establish causality definitively.

ABSTRACT The interpretation of genetic variants’ association (or not) with phenotypic resistance to newly introduced and repurposed antituberculosis drugs remains challenging, as many mutations detected by whole-genome sequencing (WGS) are classified as of uncertain significance (group 3) or not associated with resistance-interim (group 4) by the World Health Organization (WHO) mutation catalog v2. We evaluated the phenotypic impact of such variants on minimum inhibitory concentrations (MICs) for bedaquiline (BDQ), clofazimine (CFZ), delamanid (DLM), and pretomanid (PA) in Mycobacterium tuberculosis complex isolates from the multi-country DIAMA cohort in sub-Saharan Africa (SSA), which recruited RR/RS-TB patients naïve to these drugs. Among 1,475 isolates with available WGS data, 163 variants met eligibility criteria; due to viable strain unavailability, 89 isolates carrying 29 unique BDQ/CFZ-related and 60 unique DLM/PA-related variants were tested for MIC determination using broth microdilution. Additional structural modeling was performed to explore potential effects of amino-acid substitutions on protein stability. Among BDQ/CFZ-related variants, MICs above the critical concentrations (CCs) were consistently associated with mmpR5 variants, whereas variants in atpE , pepQ , and Rv1979c were not. DLM/PA variants ( ddn, fbiA–D, and fgd1 ) were frequently detected as non-fixed populations, yet rarely yielding MIC values above the CC. Predicted structural destabilization showed no consistent association with MIC values or variant fixation status. Under the conditions tested, phenotypic resistance was not detected for most group 3 and 4 variants detected by WGS. Our data provide evidence from SSA to support improved interpretation of resistance-associated mutations for new and repurposed antituberculosis drugs. IMPORTANCE Whole-genome sequencing increasingly detects Mycobacterium tuberculosis complex mutations classified by the World Health Organization (WHO) mutation catalog v2 as group 3 variants of uncertain significance or group 4 variants not associated with resistance-interim, limiting reliable prediction of resistance to new and repurposed antituberculosis drugs. By generating minimum inhibitory concentration (MIC) data for such variants identified in a multi-country sub-Saharan African cohort, this study provides phenotypic evidence to support future refinement and expansion of the WHO mutation catalog v2. Notably, mmpR5 variants associated with elevated bedaquiline/clofazimine MICs were identified in eight isolates, suggesting that some patients in this cohort may have harbored pre-existing resistance-associated variants yet remained potentially eligible for bedaquiline-containing regimens. These findings contribute to improving the interpretation of genomic resistance data and strengthening surveillance of resistance to bedaquiline, clofazimine, delamanid, and pretomanid.

Abstract Tuberculosis (TB), caused by the Mycobacterium tuberculosis complex (MTBC), remains a pressing global health challenge, with a high burden in West Africa, including The Gambia. Understanding the genetic diversity of circulating MTBC strains is essential for improving diagnosis, surveillance and treatment strategies. In this study, we characterise the population structure and drug resistance landscape of MTBC strains circulating in The Gambia over nearly two decades (2002–2021). We analysed whole-genome sequencing (WGS) data from 1,803 TB isolates. Lineage 4 (L4) was predominant (67.2%), followed by the West Africa-restricted lineage 6 (L6, 26.6%), with L4 exhibiting greater genetic diversification over time. Drug susceptibility profiling of these isolates revealed that 78% (1421/1803) were drug-susceptible, while 6.5% (119/1803) harboured resistance to first-line drugs, primarily to isoniazid, rifampicin, or both. Notably, 15.5% (282/1803) isolates carried mutations classified as having uncertain significance according to the WHO resistance catalogue. Comparative analyses revealed a lineage 6-specific ethambutol-associated mutation of uncertain significance (embC Ala307Thr) occurring at a higher frequency in Gambian isolates than in the broader West Africa region or globally. Structural modelling demonstrated that many first-line drug resistance mutations are located in highly conserved, solvent-inaccessible regions of target proteins, often impacting protein stability, suggesting a trade-off between drug resistance, bacterial fitness, and evolutionary adaptation. Together, these findings highlight the coexistence of globally widespread and regionally restricted MTBC lineages in The Gambia and reveal a substantial burden of resistance-associated mutations of uncertain significance in the WHO catalogue. Sustained genomic surveillance and region-specific interpretation of resistance mutations are essential to support End TB strategies in high-burden settings.

Background Most tuberculosis (TB) cases in The Gambia are notified in the Greater Banjul Area (GBA). We conducted an Enhanced-Case-Finding (ECF) intervention in the GBA and determined its effect on TB case notifications and ongoing TB transmission. Methods This was a cluster randomized trial in which randomly assigned intervention areas of grouped settlements received three rounds of an ECF strategy consisting of sensitization followed by auramine microscopy, whereas people with TB in control areas continued to be identified through passive case finding. People with TB were recruited at the TB diagnostic and treatment centers serving both the intervention- and control areas. The primary outcome was TB case notification rate. To exclude that an increase in notified cases, followed by a decrease in notified cases, would hide the future impact of the intervention, we tested for changes in transmission dynamics using both genetic clustering and phylodynamic methods. Results 3,047 people living with TB were recruited in the study, evenly split between intervention and control regions. No significant difference in TB case notification rates, transmission clustering or effective reproductive number was detected between intervention and control areas using either a case notification rate or phylodynamic approach. Conclusion Although we did not find evidence for decreased TB case notification nor TB transmission through the ECF strategy used, this approach is an examplar of how both classical epidemiology and genomic phylodynamics approaches can be integrated to better assess public health intervention outcomes.

Abstract Background In Rwanda, genomic surveillance identified a dominant multidrug-resistant tuberculosis (MDR-TB) strain, the R3clone, responsible for approximately 70% of rifampicin-resistant TB cases. Its presence beyond Rwanda remains unexplored. Methods Unique genetic signatures of the R3clone were defined using whole-genome sequencing of MDR-TB isolates from Rwanda. We developed a targeted qPCR assay detecting a clone-specific single-nucleotide polymorphism. With these tools, we screened isolates from neighbouring countries and public genomic repositories. Results We identified 375 R3clone isolates, including 264 from historical Rwandan collections (1991-2021), 49 from recent Rwandan diagnostic routine (2021-2024), 25 from historical Burundi isolates (2002-2013), and 37 among public repositories from several countries. The R3clone-specific qPCR showed 100% specificity in distinguishing the R3clone from other MTBC (sub-)lineages. Transmission analysis revealed cross-border transmission of the R3clone within the Great Lakes Region. Conclusion This study comprehensively assesses cross-border transmission of a dominant MDR-TB strain, highlighting the need for coordinated international surveillance. Impact statement Tuberculosis management is primarily undertaken at a national level, with associated contact tracing and public health interventions also being performed within country. Several countries have signature strain or drug resistance patterns within their Mycobacterium tuberculosis population, allowing for tracking of circulating clones within their borders. Rwanda is one such case, with the R3clone dominating the MDR-TB cases within the country. Previous studies of the R3clone have shown that improved patient management and treatment can reduce the prevalence of this clone within Rwanda. Our study confirms this decline in population size of the R3clone within Rwanda. We also show that this is not a Rwanda-restricted clone; by developing a low-cost qPCR-based detection method we uncovered this clone in Burundi and through extended search of online databases additionally found it in other neighbouring countries. Our findings demonstrate that tracking of M. tuberculosis needs to extend beyond country borders, especially in endemic regions with high levels of inter-country migration. Cross-border tracking and co-operation will enhance intervention measures and reduce cases of MDR-TB transmission. Data summary All samples sequenced in this project from the InnoR3Tb project (Rwanda and Burundi) are available via the ENA projects PRJEB106304 and PRJEB95959. The exact ENA accession codes for each sample are listed in Table S3 alongside sampling dates and countries.

In vitro experiments with Mycobacterium tuberculosis showed that clofazimine exposure selected for delamanid and pretomanid resistance and mutations in fbiA, fbiC, or fbiD-after the acquisition of Rv0678 mutations where this could be determined. Whether this is also possible in vivo and in an Rv0678 wild-type background has to be studied further. Based on the available evidence, however, we propose that nitroimidazole resistance should not be considered an exclusion criterion for the use of clofazimine.

Since 2018, the WHO recommends provision of single-dose rifampicin post-exposure prophylaxis (SDR-PEP) to contacts of leprosy patients. In the Post-ExpOsure Prophylaxis for LEprosy (PEOPLE) trial that took place in the Comoros (Anjouan and Mohéli) and Madagascar (2019–2023), single double-dose rifampicin (SDDR)-PEP administration modalities were compared. Additionally, in 16/64 villages, anti- M. leprae phenolic glycolipid-I (anti-PGL-I) IgM levels were measured for three consecutive years, in newly diagnosed leprosy patients and more than 17,000 household- and neighbourhood contacts who had been screened for signs of leprosy. To study the impact of active case finding and SDDR-PEP on M. leprae infection rates in the population, fingerstick blood of contacts was sampled before, during and after the administration of SDDR-PEP. In this serosurvey, anti-PGL-I IgM levels were measured for the first time at such large scale by local staff using a field-friendly, quantitative lateral flow assay based on the UCP-platform (UCP-LFA). Out of 53 multibacillary patients with a bacterial index of 1 or higher, 92.5% (n = 49) tested seropositive for anti- M. leprae PGL-I IgM, confirming excellent performance of the test when executed by local staff. Before SDDR-PEP administration, seroprevalence among contacts in the different villages ranged from 21.9% to 27.4% across the three study sites. After two years of active case finding and SDDR-PEP, seroprevalence was significantly lower in the population in all three study sites (11.6% to 22.8%). Longitudinal serological monitoring in initially seropositive contacts showed significant reductions in anti-PGL-I IgM levels at an individual level. This reduction in seropositivity was observed irrespective of administration of SDDR-PEP. These serological data suggest that the implemented combination of active case finding with SDDR-PEP, led to a reduction in infection levels in the population in these study sites. This large-scale field serosurvey demonstrates the usefulness of the anti-PGL-I UCP-LFA to evaluate and monitor at a population level the effects of leprosy control interventions on M. leprae transmission.

ABSTRACT This study evaluated thin-layer agar (TLA) as a faster alternative for both indirect minimum inhibitory concentration (MIC) determination of bedaquiline (BDQ) from culture isolates and direct drug-susceptibility testing (DST) from sputum samples. Indirect BDQ-MIC results from TLA were compared to the established 7H11 solid DST. Direct-TLA-DST performance was assessed using 143 baseline sputum samples from rifampicin-resistant TB cases. Direct-TLA tested susceptibility to rifampicin, isoniazid, levofloxacin, and BDQ, with results compared to Löwenstein-Jensen (LJ) and MGIT. For indirect BDQ-MIC determination, TLA accurately identified H37Rv MICs within the WHO control range (0.015–0.12μg/mL). Optimal results were obtained with standard incubation and day 7 reading of the plates. TLA correctly classified all wild-type clinical strains as BDQ-susceptible and detected 9 out of 10 BDQ-resistant strains with elevated MICs. Direct-TLA-DST detected MTB in 53.8% of samples, compared to 55.9% on LJ and 69.4% in MGIT. Uninterpretable results due to contamination or medium drying were low (4.9%). The median time to result was 15 days for smear-positive and 22 days for smear-negative samples, faster than WHO-endorsed methods. Sensitivity was 100% for rifampicin and 87.8% for isoniazid, with a specificity of 100% for all drugs except isoniazid (96.2%). No BDQ nor levofloxacin resistance was detected, thus direct TLA sensitivity could not be assessed. In conclusion, direct-TLA-DST offers a reliable and faster alternative to conventional DST methods for BDQ and other anti-TB drugs. Essentially, this technique can be operated at BioSafety Level 2, allowing decentralization of pDST for managing drug-resistant TB in settings with limited laboratory infrastructure. IMPORTANCE This paper addresses the critical need for faster direct drug-susceptibility testing (DST) on sputum, especially for bedaquiline (BDQ), which is a key drug in treating drug-resistant TB. Currently, there is a lack of rapid, reliable methods for direct BDQ testing from sputum samples, limiting timely and accurate treatment decisions and monitoring. By demonstrating the potential of thin-layer agar (TLA) for direct BDQ-MIC determination, this study offers a promising solution that could significantly improve patient care.

BACKGROUND:For decades, poor treatment options and low-quality evidence plagued care for patients with rifampin-resistant tuberculosis. The advent of new drugs to treat tuberculosis and enhanced funding now permit randomized, controlled trials of shortened-duration, all-oral treatments for rifampin-resistant tuberculosis. METHODS:We conducted a phase 3, multinational, open-label, randomized, controlled noninferiority trial to compare standard therapy for treatment of fluoroquinolone-susceptible, rifampin-resistant tuberculosis with five 9-month oral regimens that included various combinations of bedaquiline (B), delamanid (D), linezolid (L), levofloxacin (Lfx) or moxifloxacin (M), clofazimine (C), and pyrazinamide (Z). Participants were randomly assigned (with the use of Bayesian response-adaptive randomization) to receive one of five combinations or standard therapy. The primary end point was a favorable outcome at week 73, defined by two negative sputum culture results or favorable bacteriologic, clinical, and radiologic evolution. The noninferiority margin was -12 percentage points. RESULTS:Among the 754 participants who underwent randomization, 699 were included in the modified intention-to-treat analysis, and 562 in the per-protocol analysis. In the modified intention-to-treat analysis, 80.7% of the patients in the standard-therapy group had favorable outcomes. The risk difference between standard therapy and each of the four new regimens that were found to be noninferior in the modified intention-to-treat population was as follows: BCLLfxZ, 9.8 percentage points (95% confidence interval [CI], 0.9 to 18.7); BLMZ, 8.3 percentage points (95% CI, -0.8 to 17.4); BDLLfxZ, 4.6 percentage points (95% CI, -4.9 to 14.1); and DCMZ, 2.5 percentage points (95% CI, -7.5 to 12.5). Differences were similar in the per-protocol population, with the exception of DCMZ, which was not noninferior in that population. The proportion of participants with grade 3 or higher adverse events was similar across the regimens. Grade 3 or higher hepatotoxic events occurred in 11.7% of participants overall and in 7.1% of those receiving standard therapy. CONCLUSIONS:Consistent results across all the analyses support the noninferior efficacy of three all-oral shortened regimens for the treatment of rifampin-resistant tuberculosis. (Funded by Unitaid and others; endTB ClinicalTrials.gov number, NCT02754765.).

Background Leprosy remains a significant public health burden in many low- and middle-income countries, with the transmission pathways of Mycobacterium leprae remaining incompletely understood. The Research to Stop Transmission of Neglected Tropical Diseases (R2STOP) fund was established by two NGOs to address this gap by supporting research projects focused on M. leprae transmission. This article outlines R2STOP’s selection process for funding projects and summarizes the impact and findings of the resulting research, illustrating the collective progress in understanding M. leprae transmission. Methodology/Principal findings The funding priorities established by R2STOP in the call were: (i) human-to-human transmission, (ii) non-human reservoirs, (iii) host-pathogen interactions and (iv) transmission networks. R2STOP allocated a total budget of CAD one million to support research projects focused on M. leprae transmission. The selection process involved remote reviews of letters of intent and full proposals, followed by an in-person proposal review meeting where projects were evaluated based on criteria such as significance, innovation, approach, and environmental impact. Final selections were made by a Scientific Review Committee, resulting in the funding of six projects. The funded projects all yielded significant findings from exploring a variety of topics such as persistent transmission in the Comoros islands; the potential role of patients and soil in transmission; ticks’ role in transmission to hosts; biomarkers for leprosy progression; ofloxacin resistance in India; and methods to grow M. leprae on axenic media. Twenty-four MSc and PhD students were involved in the six funded research projects, and 29 scientific articles were published. Conclusions/Significance The R2STOP funding scheme played an important role in advancing our understanding of M. leprae transmission pathways and showcased the relevance of having funds allocated to this neglected aspect of leprosy control. Relevant research continues to be supported through the Leprosy Research Initiative.

The emergence of resistance is of great concern in the control of TB, especially to the new and repurposed drugs needed for the treatment of rifampicin resistance. We report a patient from South Kivu in the Eastern Democratic Republic of the Congo with primary resistance to delamanid and linezolid without treatment experience with these drugs. The identification of novel resistance mutations raises concerns about the potential global spread and poor outcomes of the WHO-recommended oral treatment regimens, highlighting the need for the urgent rollout of DST.

Background Xpert MTB/RIF Ultra (Ultra) aimed to improve the specificity in identifying rifampicin-resistant tuberculosis (RR-TB), compared to Xpert MTB/RIF. Methods In a nationwide study in Rwanda, patients diagnosed with RR-TB by Ultra between December 2021 and January 2024 underwent repeat Ultra testing, complemented by rpoB gene sequencing and phenotypic drug-susceptibility testing (pDST), serving as reference tests. Results Of 129 patients initially diagnosed with RR-TB by Ultra, only 41 (32%) had concordant rifampicin results upon repeat Ultra testing. The remaining 88 patients (68%) had unconfirmed resistance on repeat Ultra. Reference testing was available for 40 (98%) of 41 confirmed cases, all verified as true RR-TB. Among 88 unconfirmed cases, reference testing was available for 61 (69%), with 7 (11%) confirmed as true RR-TB, whereas 54 (89%) were found to have rifampicin-susceptible TB. Notably, 89% of 55 patients with very low bacillary loads on their initial Ultra had false RR-TB results, a significantly higher risk of false resistance compared to other bacillary load categories combined (risk ratio: 8.20; 95% confidence interval [CI]: 3.56-18.85; P < .001). Consequently, 53% (54/101) of initial RR patients with available reference testing received unnecessary RR-TB treatment. Conclusions Ultra represents a valuable tool for rapid RR-TB detection; however, in low prevalence settings its low positive predictive value for RR detection is largely driven by samples with very low bacillary loads. As programs expand active case-finding and early detection of asymptomatic disease, the proportion of TB detected with very low bacillary load will increase. Diagnostic algorithms require adjustments to prevent unnecessary RR-TB treatment.

RNA-based assays hold great potential for assessing viability molecularly in slow- or non-growing mycobacteria, and RNAseq has evolved into a powerful tool in infectious disease research. Such applications require efficient RNA preservation for optimal results. The performance of 70% ethanol as simpler alternative to commonly-used GTC-based storage of mycobacteria at - 80 °C was compared on cultured Mycobacterium tuberculosis H37Ra subjected to following setups: a 45 °C heat shock to test immediate stabilisation, five freeze-thaw scenarios to mimic different shipping conditions, and long-term storage at -80 °C, -20 °C, 4 °C or 30 °C for up to twelve months. Treatment with 70% ethanol yielded overall higher RNA quantities compared to GTC-TCEP and RNA integrity was maintained at -20 °C for twelve months. Both buffers are reportedly mycobactericidal and, in this study, prevented heat stress-induced transcriptomic changes, thereby conserving a transcriptomic snapshot. RNA yield and integrity remained unaltered after treatment with 70% ethanol, even with up to three freeze-thaw cycles. Based on these results, we recommend 70% ethanol over GTC-TCEP for RNA preservation of mycobacterial cultures. While freeze-thawing, short-term high-temperature and - 20 °C long-term storage results are promising, this inexpensive, widely available buffer needs further validation prior to applying it for RNA-based analysis in clinical samples.

Pulmonary tuberculosis (PTB) diagnosis primarily relies on sputum examination, which can be challenging for patients unable to produce sputum. Minimally invasive oral sampling methods, such as tongue swabs (TS), have been proposed as alternatives. We assessed the effectiveness of TS for PTB diagnosis using molecular tests. In a prospective study at two TB clinics, 99 confirmed smear-positive PTB patients provided 11 TS and one additional sputum sample (SS) for GeneXpert-Ultra (Ultra) testing at the National Reference Laboratory for Mycobacteriology. Testing was performed on a single TS (1TS), three pooled TS (3TS), and the additional SS. Additionally, we retrospectively analyzed TS from 120 participants with TB symptoms using an in-house IS6110-qPCR at the Institute of Tropical Medicine, alongside two SSs tested by fluorescence microscopy, GeneXpert-MTB/RIF (Xpert) and Ultra in Guinea. In the prospective study, among 99 smear-positive patients, Ultra detected Mycobacterium tuberculosis (MTB) in 86.9

Mycobacterium tuberculosis complex (MTBC) lineages show substantial variability in virulence, but the epidemiological consequences of this variability have not been studied in detail. Here, we aimed for a lineage-specific epidemiological characterization by applying phylodynamic models to genomic data from different countries, representing the most abundant MTBC lineages. Our results suggest that all lineages are associated with similar durations and levels of infectiousness, resulting in similar reproductive numbers. However, L1 and L6 are associated with a delayed onset of infectiousness, leading to longer periods between subsequent transmission events. Together, our findings highlight the role of MTBC genetic diversity in tuberculosis disease progression and transmission.

The Global Partnership for Zero Leprosy (GPZL) Zero Transmission Symposium (May 23-25, 2024, Bergen, Norway) brought together a diverse group of experts to discuss developments over 10 years to interrupt Mycobacterium leprae transmission, both in research and operationally. Through a well-structured and participatory agenda, research and operational approaches were discussed. The operational approaches from the symposium are described here and focus on defining optimal methods for monitoring infection transmission and prevalence using current tools; additional tools to customise implementation based on local context, such as mapping; identifying critical gaps and interventions to accelerate transmission interruption through scaled-up programmatic implementation; and expanding com-munity coverage of interventions. Recommendations were developed in diagnostics, active case detection, post-exposure prophylaxis (PEP) and treatment, antimicrobial resistance surveillance, vaccination, and social determinants of health. Recommendations in diagnostics included forming a diagnostics consortium, global initiatives (including updating WHO Guidelines) and national initiatives to optimise availability of 'point-of-care' tools, active case detection, including contact tracing, integrated programmes, and cluster-based campaigns considering strategic alignment with other disease consortia/initiatives; maximizing the use of molecular techniques and genotyping technologies; and improving epidemiological surveillance. Overall, considerable progress has been made in interrupting transmission in the last 10 years, especially at the sub-national level. Implementing symposium recommenda-tions will further accelerate interruption of M. leprae transmission.

On May 23-25, 2024, a multidisciplinary expert group met in Bergen, Norway, the site of the first description of Mycobacterium leprae (M. leprae) in 1873, to discuss advancements and remaining knowledge gaps in the transmission of M. leprae at the Global Partnership for Zero Leprosy Zero Transmission Symposium. Research and operational approaches to interruption of transmission were identified; the research approaches from the symposium are described here. Updates since a previous symposium at the National School of Tropical Medicine, Baylor College of Medicine in Houston (USA), in 2014 from these fields of research are presented here: epidemiology; microbiological diagnosis; immunodiagnostics; genotyping; geospatial mapping; leprosy elimination monitoring and transmission under low-endemic circumstances; leprosy post-exposure prophylaxis (PEP); modelling relevant to interruption of transmission of M. leprae; OneHealth; environmental transmission of M. leprae; social determinants; control programmes relevant to interruption of transmission of M. leprae; and organizations of persons affected. Progress and outstanding gaps since 2014 are identified, and recommendations for relevant research in these areas to achieve interruption of transmission are presented. These include research into human reservoirs, including platforms for field-friendly diagnostics; routes of entry/exit of M. leprae; the roles of animals or vectors in transmission; the role of social determinants in transmission; host-pathogen interactions; transmission networks; and enhanced epidemiological data. Fulfilment of these research recommendations and further understanding of which settings require intensified control efforts, will help to advance the aim of achieving complete interruption of transmission of M. leprae and the elimination of leprosy disease.