Completeness of tuberculosis (TB) notification: inventory studies and capture-recapture analyses, six European Union countries, 2014 to 2016.

BackgroundProgress towards the World Health Organization's End TB Strategy is monitored by assessing tuberculosis (TB) incidence, often derived from TB notification, assuming complete case detection and reporting. This assumption is unlikely to hold in many settings, including European Union (EU) countries.AimWe aimed to assess observed and estimated completeness of TB notification through inventory studies and capture-recapture (CRC) methodology in six EU countries: Croatia, Denmark, Finland, the Netherlands, Portugal Slovenia.MethodsWe performed record linkage, case ascertainment and CRC analyses of data collected retrospectively from at least three national TB-related registers in each country between 2014 and 2016.ResultsObserved completeness of TB notification by inventory studies was 73.9% in Croatia, 98.7% in Denmark, 83.6% in Finland, 81.6% in the Netherlands, 85.8% in Portugal and 100% in Slovenia. Subsequent CRC analysis estimated completeness of TB notification to be 98.4% in Denmark, 76.5% in Finland and 77.0% in Portugal. In Croatia, CRC analyses produced implausible results while in the Netherlands and Slovenia, it was methodologically considered not meaningful.ConclusionInventory studies and CRC methodology suggest a TB notification completeness between 73.9% and 100% in the six EU countries. Mandatory reporting by clinicians and laboratories, and cross-checking of registers, strongly contributes to accurate notification rates, but hospital episode registers likely contain a considerable proportion of false-positive TB records and are thus less useful. Further strengthening routine surveillance to count TB cases, i.e. incidence, accurately by employing record-linkage of high-quality TB registers should make CRC studies obsolete in EU countries.

Linkage to HIV care before and after the introduction of provider-initiated testing and counselling in six Rwandan health facilities.

HIV testing and counselling forms the gateway to the HIV care and treatment continuum. Therefore, the World Health Organization recommends provider-initiated testing and counselling (PITC) in countries with a generalized HIV epidemic. Few studies have investigated linkage-to-HIV-care among out-patients after PITC. Our objective was to study timely linkage-to-HIV-care in six Rwandan health facilities (HFs) before and after the introduction of PITC in the out-patient departments (OPDs). Information from patients diagnosed with HIV was abstracted from voluntary counselling and testing, OPD and laboratory registers of six Rwandan HFs during three-month periods before (March-May 2009) and after (December 2009-February 2010) the introduction of PITC in the OPDs of these facilities. Information on patients' subsequent linkage-to-pre-antiretroviral therapy (ART) care and ART was abstracted from ART clinic registers of each HF. To triangulate the findings from HF routine, a survey was held among patients to assess reasons for non-enrolment. Of 635 patients with an HIV diagnosis, 232 (36.5%) enrolled at the ART clinic within 90 days of diagnosis. Enrolment among out-patients decreased after the introduction of PITC (adjusted odds ratio, 2.0; 95% confidence interval, 1.0-4.2; p = .051). Survey findings showed that retesting for HIV among patients already diagnosed and enrolled into care was not uncommon. Patients reported non-acceptance of disease status, stigma and problems with healthcare services as main barriers for enrolment. Timely linkage-to-HIV-care was suboptimal in this Rwandan study before and after the introduction of PITC; the introduction of PITC in the OPD may have had a negative impact on linkage-to-HIV-care. Healthier patients tested through PITC might be less ready to engage in HIV care. Fear of HIV stigma and mistrust of test results appear to be at the root of these problems.

Does provider-initiated HIV testing and counselling lead to higher HIV testing rate and HIV case finding in Rwandan clinics?

BACKGROUND: Provider-initiated HIV testing and counselling (PITC) is promoted as a means to increase HIV case finding. We assessed the effectiveness of PITC to increase HIV testing rate and HIV case finding among outpatients in Rwandan health facilities (HF). METHODS: PITC was introduced in six HFs in 2009-2010. HIV testing rate and case finding were compared between phase 1 (pre-PITC) and phase 3 (PITC period) for outpatient-department (OPD) attendees only, and for OPD and voluntary counseling & testing (VCT) departments combined. RESULTS: Out of 26,367 adult OPD attendees in phase 1, 4.7% were tested and out of 29,864 attendees in phase 3, 17.0% were tested (p < 0.001). The proportion of HIV cases diagnosed was 0.25% (67/26,367) in phase 1 and 0.46% (136/29864) in phase 3 (p < 0.001). In multivariable analysis, both testing rate and case finding were significantly higher in phase 3 for OPD attendees. In phase 1 most of the HIV testing was done in VCT departments rather than at the OPD (78.6% vs 21.4% respectively); in phase 3 this was reversed (40.0% vs 60.0%; p < 0.001). In a combined analysis of VCT and OPD attendees, testing rate increased from 18.7% in phase 1 to 25.4% in phase 3, but case finding did not increase. In multivariable analysis, testing rate was significantly higher in phase 3 (OR 1.67; 95% CI 1.60-1.73), but case finding remained stable (OR 1.09; 95% CI 0.93-1.27). CONCLUSION: PITC led to a shift of HIV testing from VCT department to the OPD, a higher testing rate, but no additional HIV case finding.

Risk factors for poor tuberculosis treatment outcomes in Makassar, Indonesia.

Resistant tuberculosis is an important public health problem in South Sulawesi, Indonesia. We conducted a retrospective cohort study of 1,582 smear positive tuberculosis patients registered with the National Tuberculosis Program during 2007 in Makassar, Indonesia, to assess risk factors associated with poor tuberculosis treatment outcomes. Of the 1,582 patients, 265 had a poor treatment outcome. Of the 265 patients with a poor treatment outcome, 216 had defaulted on treatment, 7 failed treatment, 9 died and 33 transferred to another area. After adjusting for sex, age and BCG status, failure acid-fast bacilli (AFB) positive sputum to convert to AFB negative by 2-3 months was the only risk factor significantly associated with a poor treatment outcome (odds ratio 7.57; 95% CI: 1.22-47.1). We hypothesise this could represent resistant tuberculosis. Early identification of resistant tuberculosis is important and should be suspected in patients whose AFB positive sputum samples fail to convert to AFB negative by 2-3 months.

WASH, nutrition and health-seeking behavior during COVID-19 lockdowns: Evidence from rural Bangladesh.

A general lockdown to minimize to slow transmission of COVID-19 in Bangladesh came into effect on March 26th and lasted until May 30th. The lockdown had far-reaching economic implications for the population, with many facing economic hardship due to loss of income. Despite the attempt of the government to ease economic hardship by means of social safety net packages, people suffered from poor access to health services, and financial and food insecurity. This is likely to have disastrous consequences for the nutritional status of young children. This cross-sectional study measured the impact of the first general lockdown on food consumption of young children, access to water, handwashing and health seeking behavior, and the ability to maintain livelihood among households with children under the age of 5, in rural Bangladesh. The result of the analysis suggest that loss of income was reported by almost all respondents across all socio-economic groups. However, the poorest households were less likely to provide for sufficient food for their families and had to reduce consumption of food. Diet diversity and food intake-particularly animal protein sources-for young children were severely affected. On the other, increased awareness of handwashing and access to soap were also reported. The pandemic is likely to be detrimental to the nutritional status of children in Bangladesh and can exacerbate existing health inequities. Strong social safety net programs are needed to protect vulnerable populations to consequences of restrictive measures, supported in design and implementation by non-governmental organizations.

Time Trend Analysis of Tuberculosis Treatment While Using Digital Adherence Technologies-An Individual Patient Data Meta-Analysis of Eleven Projects across Ten High Tuberculosis-Burden Countries.

Worldwide, non-adherence to tuberculosis (TB) treatment is problematic. Digital adherence technologies (DATs) offer a person-centered approach to support and monitor treatment. We explored adherence over time while using DATs. We conducted a meta-analysis on anonymized longitudinal adherence data for drug-susceptible (DS) TB (n = 4515) and drug-resistant (DR) TB (n = 473) populations from 11 DAT projects. Using Tobit regression, we assessed adherence for six months of treatment across sex, age, project enrolment phase, DAT-type, health care facility (HCF), and project. We found that DATs recorded high levels of adherence throughout treatment: 80% to 71% of DS-TB patients had ≥90% adherence in month 1 and 6, respectively, and 73% to 75% for DR-TB patients. Adherence increased between month 1 and 2 (DS-TB and DR-TB populations), then decreased (DS-TB). Males displayed lower adherence and steeper decreases than females (DS-TB). DS-TB patients aged 15−34 years compared to those >50 years displayed steeper decreases. Adherence was correlated within HCFs and differed between projects. TB treatment adherence decreased over time and differed between subgroups, suggesting that over time, some patients are at risk for non-adherence. The real-time monitoring of medication adherence using DATs provides opportunities for health care workers to identify patients who need greater levels of adherence support.

Islands of Tuberculosis Elimination: An Evaluation of Community-Based Active Case Finding in North Sumatra, Indonesia.

Community-based active case finding (ACF) is needed to reach key/vulnerable populations with limited access to tuberculosis (TB) care. Published reports of ACF interventions in Indonesia are scarce. We conducted an evaluation of a multicomponent community-based ACF intervention as it scaled from one district to nine in Nias and mainland North Sumatra. Community and health system support measures including laboratory strengthening, political advocacy, sputum transport, and community awareness were instituted. ACF was conducted in three phases: pilot (18 months, 1 district), intervention (12 months, 4 districts) and scale-up (9 months, 9 districts). The pilot phase identified 215 individuals with bacteriologically positive (B+) TB, representing 42% of B+ TB notifications. The intervention phase yielded 509, representing 54% of B+ notifications and the scale-up phase identified 1345 individuals with B+ TB (56% of notifications). We observed large increases in B+ notifications on Nias, but no overall change on the mainland despite district variation. Overall, community health workers screened 377,304 individuals of whom 1547 tested positive, and 95% were initiated on treatment. Our evaluation shows that multicomponent community-based ACF can reduce the number of people missed by TB programs. Community-based organizations are best placed for accessing and engaging hard to reach populations and providing integrated support which can have a large positive effect on TB notifications.

The TB REACH Initiative: Supporting TB Elimination Efforts in the Asia-Pacific.

After many years of TB 'control' and incremental progress, the TB community is talking about ending the disease, yet this will only be possible with a shift in the way we approach the TB response. While the Asia-Pacific region has the highest TB burden worldwide, it also has the opportunity to lead the quest to end TB by embracing the four areas laid out in this series: using data to target hotspots, initiating active case finding, provisioning preventive TB treatment, and employing a biosocial approach. The Stop TB Partnership's TB REACH initiative provides a platform to support partners in the development, evaluation and scale-up of new and innovative technologies and approaches to advance TB programs. We present several approaches TB REACH is taking to support its partners in the Asia-Pacific and globally to advance our collective response to end TB.

Extra-pulmonary tuberculosis: A retrospective study of patients in Accra, Ghana.

BACKGROUND: Information on extrapulmonary TB (EPTB) patients is limited in many African countries including Ghana. The study objective was to describe the epidemiology of EPTB patients diagnosed from different categories of health facilities in Accra, Ghana compared to pulmonary TB (PTB) patients and identify risk factors for mortality among EPTB patients. METHOD: We conducted retrospective analyses of demographic and clinical data accessed from medical records of EPTB and PTB patients from different types of health facilities from June 2010 to December 2013. Factors at diagnosis associated with EPTB compared to pulmonary TB (PTB) and factors associated with treatment outcome death among EPTB patients were assessed using logistic regression. RESULTS: Out of 3,342 new TB patients ≥15 years diagnosed, 728 (21.8%) had EPTB with a male: female ratio of 1.17. The EPTB sites commonly affected were disseminated 32.8%, pleura 21%, spine 13%, and Central Nervous System (CNS) 11%. Treatment success rate for EPTB was 70.1% compared to 84.2% for PTB (p<0.001). In logistic regression, HIV positivity (adjusted Odds Ratio [aOR] 3.19; 95% confidence interval [CI] 2.69-3.79) and female gender (aOR 1.59; 95% CI 1.35-1.88) were found to be significantly associated with EPTB compared with PTB. Older age, being HIV positive (aOR 3.15; 95% CI 1.20-8.25) and having CNS TB (aOR 3.88; 95% CI 1.14-13.23) were associated with mortality among EPTB patients. While more EPTB patients were diagnosed in the tertiary hospital, health facility type was not associated with mortality. CONCLUSION: EPTB patients in Accra have a worse treatment outcome compared to PTB patients with mortality of EPTB being associated with HIV, older age and CNS TB. Being HIV positive and female gender were found to be significantly associated with EPTB. Increased awareness of these factors may facilitate early case finding and better management outcomes for these patients.

Development and validation of a predictive ecological model for TB prevalence.

Background: Nationally representative tuberculosis (TB) prevalence surveys provide invaluable empirical measurements of TB burden but are a massive and complex undertaking. Therefore, methods that capitalize on data from these surveys are both attractive and imperative. The aim of this study was to use existing TB prevalence estimates to develop and validate an ecological predictive statistical model to indirectly estimate TB prevalence in low- and middle-income countries without survey data. Methods: We included national and subnational estimates from 30 nationally representative surveys and 2 district-level surveys in India, resulting in 50 data points for model development (training set). Ecological predictors included TB notification and programmatic data, co-morbidities and socio-environmental factors extracted from online data repositories. A random-effects multivariable binomial regression model was developed using the training set and was used to predict bacteriologically confirmed TB prevalence in 63 low- and middle-income countries across Africa and Asia in 2015. Results: Out of the 111 ecological predictors considered, 14 were retained for model building (due to incompleteness or collinearity). The final model retained for predictions included five predictors: continent, percentage retreated cases out of all notified, all forms TB notification rates per 100 000 population, population density and proportion of the population under the age of 15. Cross-fold validations in the training set showed very good average fit (R-sq = 0.92). Conclusion: Predictive ecological modelling is a useful complementary approach to indirectly estimating TB burden and can be considered alongside other methods in countries with limited robust empirical measurements of TB among the general population.

Environmental risk of leptospirosis infections in the Netherlands: Spatial modelling of environmental risk factors of leptospirosis in the Netherlands.

Leptospirosis is a globally emerging zoonotic disease, associated with various climatic, biotic and abiotic factors. Mapping and quantifying geographical variations in the occurrence of leptospirosis and the surrounding environment offer innovative methods to study disease transmission and to identify associations between the disease and the environment. This study aims to investigate geographic variations in leptospirosis incidence in the Netherlands and to identify associations with environmental factors driving the emergence of the disease. Individual case data derived over the period 1995-2012 in the Netherlands were geocoded and aggregated by municipality. Environmental covariate data were extracted for each municipality and stored in a spatial database. Spatial clusters were identified using kernel density estimations and quantified using local autocorrelation statistics. Associations between the incidence of leptospirosis and the local environment were determined using Simultaneous Autoregressive Models (SAR) explicitly modelling spatial dependence of the model residuals. Leptospirosis incidence rates were found to be spatially clustered, showing a marked spatial pattern. Fitting a spatial autoregressive model significantly improved model fit and revealed significant association between leptospirosis and the coverage of arable land, built up area, grassland and sabulous clay soils. The incidence of leptospirosis in the Netherlands could effectively be modelled using a combination of soil and land-use variables accounting for spatial dependence of incidence rates per municipality. The resulting spatially explicit risk predictions provide an important source of information which will benefit clinical awareness on potential leptospirosis infections in endemic areas.

Risk factors for developing leprosy--a population-based cohort study in Indonesia.

We identified risk factors associated with increased yearly incidence rates of leprosy in five island populations. Age, sex, household size and Mycobacterium leprae-specific antibodies as well as contact factors were studied. Of 94 index patients (patients diagnosed in 2000), 43 (46%) were classified as multibacillary (MB), 17 (19%) were seropositive for PGL-1 [corrected] antibodies and 6 (7%) had M. leprae DNA in nasal swabs as determined by polymerase chain reaction (PCR) testing. All PCR positive patients were also seropositive. Forty-four of 4903 initially symptom free persons developed leprosy within 4 years, giving an incidence rate of 298 per 1000 person-years. Men had a 22 times higher risk [95% confidence interval (CI): 1.2-4.1] of developing leprosy than women. People living in households with more than 7 members had a 3.1 times higher risk (95% CI: 1.3-7.3) than households of 1-4 members. Persons who were seropositive in 2000 had a 3.8 times higher risk (95% CI: 1.1-12.6) than seronegative persons. Household contacts of MB patients had an adjusted hazard ratio (aHR) of 4.6 (95% CI: 1.6-12.9) and household contacts of PCR positive patients an aHR of 9.36 (95% CI: 2.5-34.9) compared with non-contacts. Patients with PCR positive nasal swabs, suggesting nasal excretion of M. leprae, are probably the patients with the highest transmission potential. Since all index patients who were PCR positive were also seropositive, serology seems an adequate tool to identify these patients. Preventing seropositive persons from becoming seropositive and infectious patients might break the chain of transmission.

Discordant Treatment Responses to Combination Antiretroviral Therapy in Rwanda: A Prospective Cohort Study.

INTRODUCTION: Some antiretroviral therapy naïve patients starting combination antiretroviral therapy (cART) experience a limited CD4 count rise despite virological suppression, or vice versa. We assessed the prevalence and determinants of discordant treatment responses in a Rwandan cohort. METHODS: A discordant immunological cART response was defined as an increase of <100 CD4 cells/mm3 at 12 months compared to baseline despite virological suppression (viral load [VL] <40 copies/mL). A discordant virological cART response was defined as detectable VL at 12 months with an increase in CD4 count ≥100 cells/mm3. The prevalence of, and independent predictors for these two types of discordant responses were analysed in two cohorts nested in a 12-month prospective study of cART-naïve HIV patients treated at nine rural health facilities in two regions in Rwanda. RESULTS: Among 382 patients with an undetectable VL at 12 months, 112 (29%) had a CD4 rise of <100 cells/mm3. Age ≥35 years and longer travel to the clinic were independent determinants of an immunological discordant response, but sex, baseline CD4 count, body mass index and WHO HIV clinical stage were not. Among 326 patients with a CD4 rise of ≥100 cells/mm3, 56 (17%) had a detectable viral load at 12 months. Male sex was associated with a virological discordant treatment response (P = 0.05), but age, baseline CD4 count, BMI, WHO HIV clinical stage, and travel time to the clinic were not. CONCLUSIONS: Discordant treatment responses were common in cART-naïve HIV patients in Rwanda. Small CD4 increases could be misinterpreted as a (virological) treatment failure and lead to unnecessary treatment changes.

Risk Factors of Typhoid Infection in the Indonesian Archipelago.

BACKGROUND: Knowledge of risk factors and their relative importance in different settings is essential to develop effective health education material for the prevention of typhoid. In this study, we examine the effect of household level and individual behavioural risk factors on the risk of typhoid in three Indonesian islands (Sulawesi, Kalimantan and Papua) in the Eastern Indonesian archipelago encompassing rural, peri-urban and urban areas. METHODS: We enrolled 933 patients above 10 years of age in a health facility-based case-control study between June 2010 and June 2011. Individuals suspected of typhoid were tested using the typhoid IgM lateral flow assay for the serodiagnosis of typhoid fever followed by blood culture testing. Cases and controls were defined post-recruitment: cases were individuals with a culture or serology positive result (n = 449); controls were individuals negative to both serology and culture, with or without a diagnosis other than typhoid (n = 484). Logistic regression was used to examine the effect of household level and individual level behavioural risk factors and we calculated the population attributable fraction (PAF) of removing each risk significant independent behavioural risk factor. RESULTS: Washing hands at critical moments of the day and washing hands with soap were strong independent protective factors for typhoid (OR = 0.38 95% CI 0.25 to 0.58 for each unit increase in hand washing frequency score with values between 0 = Never and 3 = Always; OR = 3.16 95% CI = 2.09 to 4.79 comparing washing hands with soap sometimes/never vs. often). These effects were independent of levels of access to water and sanitation. Up to two thirds of cases could be prevented by compliance to these practices (hand washing PAF = 66.8 95% CI 61.4 to 71.5; use of soap PAF = 61.9 95%CI 56.7 to 66.5). Eating food out in food stalls or restaurant was an important risk factor (OR = 6.9 95%CI 4.41 to 10.8 for every unit increase in frequency score). CONCLUSIONS: Major gains could potentially be achieved in reducing the incidence of typhoid by ensuring adherence to adequate hand-washing practices alone. This confirms that there is a pivotal role for 'software' related interventions to encourage behavior change and create demand for goods and services, alongside development of water and sanitation infrastructure.

Genetic, household and spatial clustering of leprosy on an island in Indonesia: a population-based study.

BACKGROUND: It is generally accepted that genetic factors play a role in susceptibility to both leprosy per se and leprosy type, but only few studies have tempted to quantify this. Estimating the contribution of genetic factors to clustering of leprosy within families is difficult since these persons often share the same environment. The first aim of this study was to test which correlation structure (genetic, household or spatial) gives the best explanation for the distribution of leprosy patients and seropositive persons and second to quantify the role of genetic factors in the occurrence of leprosy and seropositivity. METHODS: The three correlation structures were proposed for population data (n = 560), collected on a geographically isolated island highly endemic for leprosy, to explain the distribution of leprosy per se, leprosy type and persons harbouring Mycobacterium leprae-specific antibodies. Heritability estimates and risk ratios for siblings were calculated to quantify the genetic effect. Leprosy was clinically diagnosed and specific anti-M. leprae antibodies were measured using ELISA. RESULTS: For leprosy per se in the total population the genetic correlation structure fitted best. In the population with relative stable household status (persons under 21 years and above 39 years) all structures were significant. For multibacillary leprosy (MB) genetic factors seemed more important than for paucibacillary leprosy. Seropositivity could be explained best by the spatial model, but the genetic model was also significant. Heritability was 57% for leprosy per se and 31% for seropositivity. CONCLUSION: Genetic factors seem to play an important role in the clustering of patients with a more advanced form of leprosy, and they could explain more than half of the total phenotypic variance.

Prevention of leprosy using rifampicin as chemoprophylaxis.

An intervention study was implemented on five Indonesian islands highly endemic for leprosy to determine whether rifampicin can be used as chemoprophylaxis to prevent leprosy. The population was actively screened before the intervention and subsequently once a year for three years. In the control group, no chemoprophylaxis was given. In the contact group, chemoprophylaxis was only given to contacts of leprosy patients and in the blanket group to all eligible persons. The cohort consisted of 3,965 persons. The yearly incidence rate in the control group was 39/10,000; the cumulative incidence after three years was significantly lower in the blanket group (P = 0.031). No difference was found between the contact and the control groups (P = 0.93). Whether this apparent reduced leprosy incidence in the first three years in the blanket group is due to a delayed development of leprosy or a complete clearance of infection needs to be determined.

Comparative meta-analysis of tuberculosis contact investigation interventions in eleven high burden countries.

BACKGROUND: Screening of household contacts of tuberculosis (TB) patients is a recommended strategy to improve early case detection. While it has been widely implemented in low prevalence countries, the most optimal protocols for contact investigation in high prevalence, low resource settings is yet to be determined. This study evaluated contact investigation interventions in eleven lower and middle income countries and reviewed the association between context or program-related factors and the yield of cases among contacts. METHODS: We reviewed data from nineteen first wave TB REACH funded projects piloting innovations to improve case detection. These nineteen had fulfilled the eligibility criteria: contact investigation implementation and complete data reporting. We performed a cross-sectional analysis of the percentage yield and case notifications for each project. Implementation strategies were delineated and the association between independent variables and yield was analyzed by fitting a random effects logistic regression. FINDINGS: Overall, the nineteen interventions screened 139,052 household contacts, showing great heterogeneity in the percentage yield of microscopy confirmed cases (SS+), ranging from 0.1% to 6.2%). Compared to the most restrictive testing criteria (at least two weeks of cough) the aOR's for lesser (any TB related symptom) and least (all contacts) restrictive testing criteria were 1.71 (95%CI 0.94-3.13) and 6.90 (95% CI 3.42-13.93) respectively. The aOR for inclusion of SS- and extra-pulmonary TB was 0.31 (95% CI 0.15-0.62) compared to restricting index cases to SS+ TB. Contact investigation contributed between <1% and 14% to all SS+ cases diagnosed in the intervention areas. CONCLUSIONS: This study confirms that high numbers of active TB cases can be identified through contact investigation in a variety of contexts. However, design and program implementation factors appear to influence the yield of contact investigation and its concomitant contribution to TB case detection.

Population survey to determine risk factors for Mycobacterium leprae transmission and infection.

BACKGROUND: Not every leprosy patient is equally effective in transmitting Mycobacterium leprae. We studied the spatial distribution of infection (using seropositivity as a marker) in the population to identify which disease characteristics of leprosy patients are important in transmission. METHODS: Clinical data and blood samples for anti-M. leprae ELISA were collected during a cross-sectional survey on five Indonesian islands highly endemic for leprosy. A geographic information system (GIS) was used to define contacts of patients. We investigated spatial clustering of patients and seropositive people and used logistic regression to determine risk factors for seropositivity. RESULTS: Of the 3986 people examined for leprosy, 3271 gave blood. Seroprevalence varied between islands (1.7-8.7%) and correlated significantly with leprosy prevalence. Five clusters of patients and two clusters of seropositives were detected. In multivariate analysis, seropositivity significantly differed by leprosy status, age, sex, and island. Serological status of patients appeared to be the best discriminator of contact groups with higher seroprevalence: contacts of seropositive patients had an adjusted odds ratio (aOR) of 1.75 (95% CI 0.922-3.31). This increased seroprevalence was strongest for contact groups living < or =75 m of two seropositive patients (aOR = 3.07; 95% CI 1.74-5.42). CONCLUSIONS: In this highly endemic area for leprosy, not only household contacts of seropositive patients, but also people living in the vicinity of a seropositive patient were more likely to harbour antibodies against M. leprae. Through measuring the serological status of patients and using a broader definition of contacts, higher risk groups can be more specifically identified.