Karonga District, in northern Malawi, is among the most thoroughly studied areas in the world with respect to leprosy. This report traces the story of leprosy work in the district over the past five decades, describing its contributions to our understanding of the natural history of the disease as well its changing pattern as it declined to very low level. It concludes by comparing these patterns and trends to observations in other leprosy endemic populations.

Leprosy is in decline in most endemic countries around the world. A Lepra-supported project in Malawi has evolved over the last 50 years from a unit initially dedicated solely to the study of leprosy epidemiology and control, to one that can apply its expertise and experience in an ever-widening array of public health challenges. The ultimate result of this process, the reduction of leprosy to very low levels in Karonga (averaging only 1 case per year for the last decade, most of them from outside the district) and the evolution of a leprosy project into a major national resource for medical and public health research in Malawi, may serve as a model for how the leprosy endgame can be managed.

The Global Polio Eradication Initiative made immense progress after its establishment in 1988 as a consequence of high coverage with various poliovirus vaccines in all populations of the world. Problems have arisen in recent years, however, related to security issues in some countries, to the circulation of vaccine-derived polioviruses, and to the recognition that individuals with certain immune deficiencies can remain infected and infectious for many months or years. As natural infection and different vaccines have different effects on the immune system, the patterns of humoral and mucosal immunity to polioviruses in the world today are complex but are crucial to the ultimate success of the eradication initiative. This paper describes the background of the current situation and current immunological patterns and discusses their implications for managing population immunity to polioviruses in the years ahead.

Vaccines against different SARS-CoV-2 variants have been approved, but continued surveillance is needed to determine when the antigen composition of vaccines should be updated, together with clinical studies to assess vaccine efficacy.

Vaccines are given to people to protect them against disease. They are also given to reduce transmission of infection, thereby preventing disease even in non-vaccinated persons, and thus protecting communities. The extension of perspective from individuals to their communities is the business of public health. The use of an increasing number of different vaccines, in all populations of the world, represents a major, evolving, and highly complicated intervention into human ecology.This chapter describes the history, theory and practical real-world experience of vaccination in control of infectious diseases in populations. It discusses how the presence of vaccinated, directly protected, immune individuals can reduce infection transmission and thereby provide indirect protection to susceptibles remaining in the population. The extent and implications of such protection are a function of several factors, such as the nature of the immunity, the transmissibility of the infection, the prevalence of immune individuals in the population, and the pattern of mixing and contact between members of the population. Under particular conditions, the combination of direct and indirect protection can lead to global eradication of an infection and disease, as was achieved with smallpox, and as currently being attempted, with polio. After reviewing the theory which has evolved to describe these mechanisms, the chapter describes the complexity of the programs and effects which have been observed with 19 important infectious diseases and their specific vaccines.

Sri Lanka achieved the leprosy elimination goal set by the WHO in 1995. The success in achieving this goal was mainly due to an effective social marketing campaign carried out in the late nineteen-eighties by the Anti-Leprosy Campaign programme. However, the WHO now identifies the country as a high-burden country in the region. This paper aims to present the pattern and trends of leprosy in Sri Lanka from 1985 to 2021 and the characteristics associated with changes over time. From the trends we have observed, we believe that more awareness programmes (similar to the early social marketing campaign) and targeted active case-finding activities will help to interrupt transmission in the country.

OBJECTIVES:Investigate risk factors for SARS-CoV-2 infections in school students and staff. METHODS:In the 2020/2021 school year, we administered polymerase chain reaction, antibody tests, and questionnaires to a sample of primary and secondary school students and staff, with data linkage to COVID-19 surveillance. We fitted logistic regression models to identify the factors associated with infection. RESULTS:We included 6799 students and 5090 staff in the autumn and 11,952 students and 4569 staff in the spring/summer terms. Infections in students in autumn 2020 were related to the percentage of students eligible for free school meals. We found no statistical association between infection risk in primary and secondary schools and reported contact patterns between students and staff in either period in our study. Using public transports was associated with increased risk in autumn in students (adjusted odds ratio = 1.72; 95% confidence interval 1.31-2.25) and staff. One or more infections in the same household during either period was the strongest risk factor for infection in students and more so among staff. CONCLUSION:Deprivation, community, and household factors were more strongly associated with infection than contacts patterns at school; this suggests that the additional school-based mitigation measures in England in 2020/2021 likely helped reduce transmission risk in schools.

In 2019, a community-based, cross-sectional carriage survey and a seroprevalence survey of 1,216 persons 1–55 years of age were conducted in rural Vietnam to investigate the mechanism of diphtheria outbreaks. Seroprevalence was further compared with that of an urban area that had no cases reported for the past decade. Carriage prevalence was 1.4%. The highest prevalence, 4.5%, was observed for children 1–5 years of age. Twenty-seven asymptomatic Coerynebacterium diphtheriae carriers were identified; 9 carriers had tox gene–bearing strains, and 3 had nontoxigenic tox gene–bearing strains. Child malnutrition was associated with low levels of diphtheria toxoid IgG, which might have subsequently increased child carriage prevalence. Different immunity patterns in the 2 populations suggested that the low immunity among children caused by low vaccination coverage increased transmission, resulting in symptomatic infections at school-going age, when vaccine-induced immunity waned most. A school-entry booster dose and improved infant vaccination coverage are recommended to control transmissions.

Background The importance of remote infection with M . tuberculosis as a cause of tuberculosis disease (TB) is unclear, with limited evidence of impact on TB rates beyond 10 years. Our objective was to assess rates of tuberculosis over 30 years by M . tuberculosis infection status at baseline in Karonga District, Northern Malawi. Materials and methods Population-based surveys of tuberculin skin testing (TST) from the 1980s were linked with follow-up and TB surveillance in Karonga district. We compared rates of microbiologically-confirmed TB by baseline TST induration <5mm (no evidence of M . tuberculosis infection) and those with baseline TST >17mm (evidence of M . tuberculosis infection), using hazard ratios by time since baseline and attributable risk percent. The attributable risk percent was calculated to estimate the proportion of TB in those infected that can be attributed to that prior infection. We analysed whole genome sequences of M . tuberculosis strains to identify recent transmission. Results Over 412,959 person-years, 208 incident TB episodes were recorded. Compared to the small induration group, rates of TB were much higher in the first two years in the large induration group, and remained higher to 20 years: age, sex and area-adjusted hazard ratios (HR) 2–9 years post-TST 4.27 (95%CI 2.56–7.11); 10–19 years after TST 2.15 (1.10–4.21); ≥20 years post-TST 1.88 (0.76–4.65). The attributable risk percent of remote infection was 76.6% (60.9–85.9) 2–9 years post-TST, and 53.5% (9.1–76.2) 10–19 years post-TST. Individuals with large TST indurations had higher rates of unique-strain TB (HR adjusted for age, sex and area = HR 6.56 (95% CI 1.96–22.99)), suggesting disease following remote infection, but not of linked-strain TB (recent transmission). Conclusions M . tuberculosis infection can increase the risk of TB far beyond 10 years, accounting for a substantial proportion of TB occurring among those remotely infected.

Background: SARS-CoV-2 infection rates are likely to be underestimated in children because of asymptomatic or mild infections. We aim to estimate national and regional prevalence of SARS-CoV-2 antibodies in primary (4-11 years old) and secondary (11-18 years old) school children between 10 November and 10 December 2021.Methods: Cross-sectional surveillance in England using two-stage sampling, firstly stratifying into regions and selecting local authorities, then selecting schools according to a stratified sample within selected local authorities. Participants were sampled using a novel oral fluid-validated assay for SARS-CoV-2 spike and nucleocapsid IgG antibodies.Results: 4980 students from 117 state-funded schools (2706 from 83 primary schools, 2274 from 34 secondary schools) provided a valid sample. After weighting for age, sex, and ethnicity, and adjusting for assay accuracy, the national prevalence of SARS-CoV-2 antibodies in primary school students, who were all unvaccinated, was 40.1% (95% CI 37.3-43.0). Antibody prevalence increased with age (p < 0.001) and was higher in urban than rural schools (p = 0.01). In secondary school students, the adjusted, weighted national prevalence of SARS-CoV-2 antibodies was 82.4% (95% CI 79.5-85.1); including 71.5% (95% CI 65.7-76.8) in unvaccinated and 97.5% (95% CI 96.1-98.5) in vaccinated students. Antibody prevalence increased with age (p < 0.001), and was not significantly different in urban versus rural students (p = 0.1). Conclusions: In November 2021, using a validated oral fluid assay, national SARS-CoV-2 seroprevalence was estimated to be 40.1% in primary school students and 82.4% in secondary school students. In unvaccinated children, this was approximately threefold higher than confirmed infections highlighting the importance of seroprevalence studies to estimate prior exposure.Data availability: Deidentified study data are available for access by accredited researchers in the ONS Secure Research Service (SRS) for accredited research purposes under part 5, chapter 5 of the Digital Economy Act 2017. For further information about accreditation, contact Research.support@ons.gov.uk or visit the SRS website. Crown Copyright (c) 2023 Published by Elsevier Ltd on behalf of The British Infection Association. This is an open access article under the CC BY license (http://creativecommons.org/licenses/by/4.0/).

Leprosy is a chronic infection of the skin and peripheral nerves caused by Mycobacterium leprae. Despite recent improvements in disease control, leprosy remains an important cause of infectious disability globally. Large-scale genetic association studies in Chinese, Vietnamese and Indian populations have identified over 30 susceptibility loci for leprosy. There is a significant burden of leprosy in Africa, however it is uncertain whether the findings of published genetic association studies are generalizable to African populations. To address this, we conducted a genome-wide association study (GWAS) of leprosy in Malawian (327 cases, 436 controls) and Malian (247 cases, 368 controls) individuals. In that analysis, we replicated five risk loci previously reported in China, Vietnam and India; MHC Class I and II, LACC1 (2 independent loci) and SLC29A3. We further identified a novel leprosy susceptibility locus at 10q24 (rs2015583: combined p=8.81x10-9; OR=0.51 [95% CI 0.40-0.64]). The leprosy risk locus is a determinant of ACTR1A RNA expression in CD4+ T cells (posterior probability of colocalization - PP=0.96). Furthermore, it demonstrates pleiotropy with established risk loci for inflammatory bowel disease and atopic disease. Reduced ACTR1A expression decreases susceptibility to leprosy and atopy but increases risk of inflammatory bowel disease. A shared genetic architecture for leprosy and inflammatory bowel disease has been previously described. We expand on this, strengthening the evidence that selection pressure driven by leprosy has shaped the evolution of autoimmune and atopic disease in modern populations. More broadly, our data highlights the importance of defining the genetic architecture of disease across genetically diverse populations, and that disease insights derived from GWAS in one population may not translate to all affected populations.

Leprosy is a chronic infection of the skin and peripheral nerves caused by Mycobacterium leprae . Despite recent improvements in disease control, leprosy remains an important cause of infectious disability globally. Large-scale genetic association studies in Chinese, Vietnamese and Indian populations have identified over 30 susceptibility loci for leprosy. There is a significant burden of leprosy in Africa, however it is uncertain whether the findings of published genetic association studies are generalizable to African populations. To address this, we conducted a genome-wide association study (GWAS) of leprosy in Malawian (327 cases, 436 controls) and Malian (247 cases, 368 controls) individuals. In that analysis, we replicated four risk loci previously reported in China, Vietnam and India; MHC Class I and II, LACC1 and SLC29A3 . We further identified a novel leprosy susceptibility locus at 10q24 (rs2015583; combined p = 8.81 × 10 −9 ; OR = 0.51 [95% CI 0.40 − 0.64]). Using publicly-available data we characterise regulatory activity at this locus, identifying ACTR1A as a candidate mediator of leprosy risk. This locus shows evidence of recent positive selection and demonstrates pleiotropy with established risk loci for inflammatory bowel disease and childhood-onset asthma. A shared genetic architecture for leprosy and inflammatory bowel disease has been previously described. We expand on this, strengthening the hypothesis that selection pressure driven by leprosy has shaped the evolution of autoimmune and atopic disease in modern populations. More broadly, our data highlights the importance of defining the genetic architecture of disease across genetically diverse populations, and that disease insights derived from GWAS in one population may not translate to all affected populations.

Background: Diphtheria cases reported in Central Vietnam since 2013 were mainly in children aged 6-15 years, which may reflect an immunity gap. There is little information on population immunity against diphtheria in countries without a school-entry booster dose. We aimed to measure the age-stratified seroprevalence of anti-diphtheria toxoid antibodies, quantify the change in antibody levels in individuals over time, and estimate the length of protective immunity after vaccination in well-vaccinated communities in Vietnam.Methods: An age-stratified seroprevalence survey among individuals aged 0-55 years was conducted at Nha Trang, Vietnam. The same participants were followed up after two years to quantify the change in antibody levels. IgG was measured using ELISA. The length of protective immunity after vaccination was estimated using a mixed-effect linear regression model with random intercept.Results: Overall seroprevalence was 26% (95%CI:20-32%). Age-stratified seroprevalence was 68% (95%CI:4-11%), 7% (95%CI:4-11%), 12% (95%CI:7-19%), 33% (95%CI:27-40%), and 28% (95%CI:17-43%) among those aged ≤5, 6-15,16-25, 26-35, and 36-55 years, respectively. The antibody levels declined by 47% (95%CI:31-59%) over two years, and the predicted duration of vaccine-derived protective immunity after receiving four doses was 4.3 years (95%CI:3.5–5.3) among participants aged six years or younger.Conclusion: Given the low seroprevalence and short period of vaccine protection, a school-entry booster dose (5-7 years) is recommended in Vietnam.

Background Important gaps exist in our understanding of Mycobacterium tuberculosis transmission, especially in high HIV prevalence settings. There is significant uncertainty about where most transmission takes place in the community, impeding control efforts. M. tuberculosis infection in young children is a sensitive indicator of recent transmission and may provide a means of identifying locales of community transmission. We estimate the causal effect of church attendance on incident M. tuberculosis infection in young children. Methods Children aged under six years residing within a demographic surveillance site in Malawi were recruited. Tuberculin skin testing (TST) was performed at baseline and repeated after 1–2 years. At the time of the 2nd TST, structured guardian interviews were undertaken to ascertain any known contact with tuberculosis within the previous 12–18 months. Detailed household socioeconomic and demographic data were available. Very few children had never attended church in the previous year (<4%) so the unexposed group was combined with the next category (1–3 attendances) to form the baseline. Incident infection was defined as an increase in TST induration of ≥13mm from 1st TST to 2nd TST among those with indurations of <10mm at baseline (based on mixture analysis). We used hierarchical targeted maximum likelihood estimation (TMLE) to estimate the causal effect of church attendance on infection incidence accounting for clustering at the community-level. Confounders included age, sex, household socioeconomic status and time between TSTs. Results 2349 children were eligible for inclusion, of whom 2019 (86%) had a 2nd TST placed and data on church attendance. 66 (3.2%: 95% CI 2.5–4.1) children had evidence of TST-conversion; 3/1795 (1.4%: 95% CI 0.3 – 4.0) among those with <4 attendances and 633.3%: 95% CI 2.5–4.2) in those with ≥ 4 attendances. The estimated adjusted risk ratio was 2.8 (95%CI 1.2 – 6.7; p-value 0.023) for church attendance compared to baseline group. Conclusion High levels of church attendance (≥ 4 per year) increased the risk of incident infection by 2.8-fold compared to church attendance of less than 4 attendances per year in young children in rural Malawi. Simple infection control practices, such as opening windows or even holding congregations in outdoor spaces, may be highly beneficial in mitigating the risk of community M. tuberculosis transmission and other respiratory/airborne pathogens.

Background Trials of BCG vaccination to prevent or reduce severity of COVID-19 are taking place in adults, some of whom have been previously vaccinated, but evidence of the beneficial, non-specific effects of BCG come largely from data on mortality in infants and young children, and from in-vitro and animal studies, after a first BCG vaccination. We assess all-cause mortality following a large BCG revaccination trial in Malawi. Methods The Karonga Prevention trial was a population-based, double-blind, randomised controlled in Karonga District, northern Malawi, that enrolled participants between January, 1986, and November, 1989. The trial compared BCG (Glaxo-strain) revaccination versus placebo to prevent tuberculosis and leprosy. 46 889 individuals aged 3 months to 75 years were randomly assigned to receive BCG revaccination (n=23 528) or placebo (n=23 361). Here we report mortality since vaccination as recorded during active follow-up in northern areas of the district in 1991-94, and in a demographic surveillance follow-up in the southern area in 2002-18. 7389 individuals who received BCG (n=3746) or placebo (n=3643) lived in the northern follow-up areas, and 5616 individuals who received BCG (n=2798) or placebo (n=2818) lived in the southern area. Year of death or leaving the area were recorded for those not found. We used survival analysis to estimate all-cause mortality. Findings Follow-up information was available for 3709 (99.0%) BCG recipients and 3612 (99.1%) placebo recipients in the northern areas, and 2449 (87.5%) BCG recipients and 2413 (85.6%) placebo recipients in the southern area. There was no difference in mortality between the BCG and placebo groups in either area, overall or by age group or sex. In the northern area, there were 129 deaths per 19 694 person-years at risk in the BCG group (6.6 deaths per 1000 person-years at risk [95% CI 5.5-7.8]) versus 133 deaths per 19 111 person-years at risk in the placebo group (7.0 deaths per 1000 person-years at risk [95% CI 5.9-8.2]; HR 0.94 [95% CI 0.74-1.20]; p=0.62). In the southern area, there were 241 deaths per 38 399 person-years at risk in the BCG group (6.3 deaths per 1000 person-years at risk [95% CI 5.5-7.1]) versus 230 deaths per 38 676 person-years at risk in the placebo group (5.9 deaths per 1000 person-years at risk [95% CI 5.2-6.8]; HR 1.06 [95% CI 0.88-1.27]; p=0.54). Interpretation We found little evidence of any beneficial effect of BCG revaccination on all-cause mortality. The high proportion of deaths attributable to non-infectious causes beyond infancy, and the long time interval since BCG for most deaths, might obscure any benefits. Copyright (C) 2021 The Author(s). Published by Elsevier Ltd.

BackgroundA large, double-blind, randomised, placebo-controlled trial of repeat BCG found 49% efficacy against leprosy but no protection against tuberculosis after 6–9 years’ follow-up in 1995. We report here additional follow-up, which resulted in greatly increased tuberculosis case numbers, and allowed subgroup analysis.MethodsNearly 47 000 individuals of all ages living in northern Malawi with a BCG vaccine scar were randomly assigned (1:1) between 1986 and 1989 to receive a second BCG or placebo. The investigators and project staff remained masked to all interventions. Enhanced passive surveillance ensured ascertainment of tuberculosis and leprosy to the end of 2018. Tuberculosis case definitions included rigorous microbiological or histological confirmation. Prespecified subgroup analyses were by tuberculosis type, age at vaccination, time since vaccination, previous tuberculin reactivity, HIV status and Mycobacterium tuberculosis lineage. The original trial is registered with ISRCTN registry, ISRCTN11311670.FindingsIn follow-up until Dec 31, 2018, 824 participants had developed tuberculosis, including 786 with pulmonary disease, of whom 383 (63%) of 607 with known HIV status were HIV positive. There was no effect of a second BCG overall (odds ratio [OR] 0·92; 95% CI 0·80–1·05), or for pulmonary (0·93; 0·81–1·07), or lymph node tuberculosis (0·60; 0·31–1·17). The OR was lower for those with known HIV-negative tuberculosis (0·77; 0·59–1·00), for those vaccinated as children (aged <5 years, 0·74; 0·41–1·35; aged 5–14 years, 0·77; 0·60–0·99), and for cases arising at least 20 years after vaccination (0·79; 0·63–1·01). There were no differences by tuberculin status at vaccination, or lineage. There was no evidence of protection against leprosy beyond 10 years after vaccination (although there have been only nine diagnostically certain cases since 1995).InterpretationThere was no evidence that repeat BCG vaccination provides appreciable protection against overall tuberculosis in this rural African population with a high prevalence of HIV. Subgroup effects should not be overinterpreted given the multiple analyses done. However, the evidence for modest protection against HIV-negative tuberculosis, and for a delayed benefit in those vaccinated as children, is consistent with other observations in the literature.FundingLEPRA, Wellcome Trust, Bill & Melinda Gates Foundation.

Since the emergence and spread of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), which has caused the COVID-19 pandemic, many countries have rapidly expanded their viral surveillance systems. Wastewater sampling has been increasingly implemented, as substantial quantities of SARS-CoV-2 are shed in the stool of infected individuals.1Xu Y Li X Zhu B et al.Characteristics of pediatric SARS-CoV-2 infection and potential evidence for persistent fecal viral shedding.Nat Med. 2020; 26: 502-505Crossref PubMed Scopus (1024) Google Scholar So far, wastewater sampling has retrospectively shown that virus is present in cities several months before large COVID-19 outbreaks,2Kelland K Italy sewage study suggests COVID-19 was there in December 2019. Reuters, June 19, 2020https://uk.reuters.com/article/us-health-coronavirus-italy-sewage-idUKKBN23Q1J9Date accessed: June 22, 2020Google Scholar that there is a correlation between quantitative RT-PCR data and the reported incidence of cases,3Wu F Xiao A Zhang J et al.SARS-CoV-2 titers in wastewater are higher than expected from clinically confirmed cases.medRxiv. 2020; (published online April 7.) (preprint)https://doi.org/10.1101/2020.04.05.20051540Google Scholar and that the presence of SARS-CoV-2 in wastewater is ubiquitous.4Medema G Heijnen L Elsinga G Italiaander R Brouwer A Presence of SARS-Coronavirus-2 in sewage.medRxiv. 2020; (published online March 30.) (preprint)https://doi.org/10.1101/2020.03.29.20045880Google Scholar There are numerous benefits of wastewater sampling, but the collection and interpretation of data is an emerging field. Within the Global Polio Eradication Initiative, wastewater sampling has successfully been used to detect polioviruses and inform eradication for several decades.5Asghar H Diop OM Weldegebriel G et al.Environmental surveillance for polioviruses in the global polio eradication initiative.J Infect Dis. 2014; 210: S294-S303Crossref PubMed Scopus (230) Google Scholar This virological analysis and investigation of wastewater has been done by the Global Polio Laboratory Network and independent laboratories. Here, we highlight several challenges of wastewater sampling for SARS-CoV-2 and outline lessons that can be learnt from polio eradication. Interpretation of a single positive wastewater sample is difficult; longitudinal sampling alongside clinical surveillance is more informative. One positive sample merely suggests that at least one individual has shed virus upstream from the sampling site, and does little to inform epidemiology. Quantitative data (eg, quantitative PCR, metagenomics), and longitudinal sampling from the same site can provide more context. In the COVID-19 pandemic, the interpretation of positive samples will vary according to local assessment of the epidemiology: from an importation event to continued infection in the community. Development of protocols for interpreting and responding to positive SARS-CoV-2 samples are essential even in the early stages of use. RNA from the virus has been detected in stool (via RT-PCR amplification), but there is little evidence for infectious virus in stool,1Xu Y Li X Zhu B et al.Characteristics of pediatric SARS-CoV-2 infection and potential evidence for persistent fecal viral shedding.Nat Med. 2020; 26: 502-505Crossref PubMed Scopus (1024) Google Scholar, 6Xiao F Sun J Xu Y et al.Infectious SARS-CoV-2 in feces of patient with severe COVID-19.Emerg Infect Dis. 2020; (published online May 18.)https://doi.org/10.3201/eid2608.200681Crossref Scopus (356) Google Scholar meaning that whether stool is a source of new infections is unclear. Sample site characteristics affect virus detection and require further study. Locations include the entrances of sewage treatment works, upstream pumping stations, or direct collection at rivers or latrines. Industry effluence, runoff from excess rain, and the pH of the sample7Hamisu AW Blake IM Sume G et al.Characterizing environmental surveillance sites in Nigeria and their sensitivity to detect poliovirus and other enteroviruses.J Infect Dis. 2020; (published online April 9.)https://doi.org/10.1093/infdis/jiaa175Crossref PubMed Scopus (10) Google Scholar can all affect sample quality, which might influence the ability to detect and isolate virus. The method of sampling (eg, 24-h composite samples vs periodic grab samples), population demographics of the catchment area, and local epidemiological factors are important for planning environmental surveillance. The method and volume of sample is also important: several approaches (eg, bag filtration and composite sampling) are used to increase the volume of a sample.8Manor Y Handsher R Halmut T et al.Detection of poliovirus circulation by environmental surveillance in the absence of clinical cases in Israel and the Palestinian authority.J Clin Microbiol. 1999; 37: 1670-1675Crossref PubMed Google Scholar Although large sample volumes might increase identification of virus in wastewater, this can make samples increasingly intractable to handle and process in laboratories. Wastewater sampling in cities requires good maps of sewer networks to understand what population is being represented. In very mobile populations (exemplified in Pakistan) sampling might indicate the presence of virus but not the affected population. Outside of dense populations there are fewer converging sewer networks that enable informative wastewater sampling; alternative sampling strategies for remote settings are a recognised need. Laboratory methods should be validated, and for the assays that are used, analytical specificity and limits of detection should be reported.9Lodder WJ Buisman AM Rutjes SA Heijne JC Teunis PF de Roda Husman AM Feasibility of quantitative environmental surveillance in poliovirus eradication strategies.Appl Environ Microbiol. 2012; 78: 3800-3805Crossref PubMed Scopus (53) Google Scholar Suitable process controls should be defined to validate results, identify false negatives, and minimise cross-contamination. In polio surveillance, isolation of the related non-polio enteroviruses (a group of ubiquitous enteric viruses) has been a useful quality indicator for field samples and testing performance. WHO protocols suggest that at least 10–30% of samples should reveal non-polio enteroviruses, and sites can be rejected if isolation is not possible. A clear separation in sample handling and processing is needed to reduce the risk of cross-contamination. Generally, samples are processed within biosafety level two laboratory conditions, separate from clinical samples, where the standard process involves a two-phase separation procedure (for virus concentration), followed by virus culture and isolation, as well as molecular methods that offer genome detection. Increasingly, specialist laboratories are also adopting modern sequence-based methods for wastewater surveillance, such as metagenomics or nanopore sequencing,10Shaw AG Majumdar M Troman C et al.Rapid and sensitive direct detection and identification of poliovirus from stool and environmental surveillance samples using nanopore sequencing.bioRxiv. 2020; (published online April 28.) (preprint)https://doi.org/10.1101/2020.04.27.053421Google Scholar which generates high-resolution genomic information that offers detailed insights into possible virus origins. Despite the challenges, wastewater sampling has long been an important supplement to clinical surveillance in polio eradication and has the potential to inform the epidemiology of COVID-19. Wastewater sampling can act as an early warning system for local infection, and support clinical surveillance to confirm local elimination through negative samples. To be an informative mode of surveillance, it will be essential to set minimum criteria for surveillance sites, develop a consistent sampling strategy, establish laboratory testing protocols to enhance sensitivity and minimise the risks of cross-contamination, and to collaborate internationally. We declare no competing interests.

Background: There is continued uncertainty over trends of leprosy, including in areas with low incidence, where it may be possible to identify areas where M leprae is no longer transmitted or where it no longer causes disease. WHO has reported data on leprosy in the European Region only since 2015. Methods: Data reported to WHO and published in the Weekly Epidemiological Record were reviewed, Data from five districts in northern Portugal were collected from the National General Directorate of Health and Municipal Health Authorities. Results: Basic information on 133 leprosy cases has been reported to WHO by thirteen of the 54 states in the European Union since 2015. Data on place of birth of the cases were reported by ten states since 2016, implying eleven cases possibly attributable to transmission within Europe. Detailed but incomplete data on 38 leprosy cases notified in northern Portugal 1990-2018 are described and discussed. Of those cases which appear to have been autochthonous, none were born after 1966, none were notified after 2007, and the only three notifications after 2005 were for relapses. Conclusions: Data on leprosy in the European Region are obviously incomplete. The large majority of cases now detected are attributable to infections contracted abroad, but a small number of cases possibly attributable to local transmission are still being identified. Analysis of data from five districts in northern Portugal indicate that this region is no longer endemic for the disease, and that transmission in the area is likely to have ceased at least 40 years ago. The methods illustrated in this paper could be applied to data on leprosy in other regions of Europe, to better define the geographic limits of leprosy today.

Individual level data on vaccine allocation and outcome (dates of death or loss to follow-up) in those actively followed in two areas following the original vaccine trial in 1986-89.