Sexually transmitted infections (STIs) and blood-borne viruses (BBVs) impose a global health and economic burden. International travellers facilitate the spread of infectious diseases, including STIs. Hence, this review assessed the prevalence/proportionate morbidity of travellers with STIs and sexually transmitted BBVs and factors associated with the infection in this population. PubMed, Scopus, Web of Science, Cumulative Index to Nursing and Allied Health Literature (CINAHL), Embase and Cochrane Library were searched from inception of the databases until November 2022. Published analytical observational studies reporting the prevalence/proportionate morbidity of travellers with STIs and factors associated with STIs by type of traveller [i.e. tourists, business travellers, students, visiting friends or relatives (VFRs), international truck drivers, backpackers, expatriates and men who have sex with men (MSM)] were included. The selection of articles, data extraction and risk of bias assessment were conducted by two independent reviewers. Meta-analyses were conducted for each STI by clinical presentation and type of traveller. Thirty-two studies (n = 387 731 travellers) were included; 19 evaluated the proportionate morbidity of STIs among symptomatic travellers, while 13 examined the prevalence of STIs in asymptomatic travellers. The highest proportionate morbidity was found among VFRs (syphilis, 1.67%; 95% CI: 1.03–2.81%), backpackers (Chlamydia trachomatis, 6.58%; 95% CI: 5.96–7.25%) and MSM (HIV [2.50%;95% CI: 0.44–12.88%], gonorrhoea [4.17%; 95% CI: 1.1.5–13.98%], lymphogranuloma venereum [4.17%;95% CI: 1.1.5–13.98%] and HAV [20.0%; 95% CI: 14.99–26.17%]). The highest prevalence of STIs among asymptomatic were found in MSM (HIV [25.94%; 95% CI: 22.21–30.05%] and HBV [24.90%; 95% CI: 21.23–28.96%]) and backpackers (C. trachomatis, 3.92%; 95% CI: 2.72–5.32%). Short duration of the trip (<1 month), not having pre-travel consultation, travelling to Southeast Asia and being unvaccinated for HBV were identified as risk factors for STIs. Strategies to prevent STIs and sexually transmitted BBVs should be discussed at pre-travel consultations, and recommendations should be prioritized in high-risk groups of travellers, such as backpackers, VFRs and MSMs. Additionally, healthcare providers should tailor recommendations for safe sex practices to individual travellers’ unique needs.

The World Health Organization (WHO) has validated 21 countries as having eliminated lymphatic filariasis (LF) as a public health problem. Post-validation surveillance (PVS) is required in countries where LF has been eliminated. Tonga eliminated LF in 2017, but no PVS strategy has been established. We aimed to identify any persistent LF transmission in Tonga in 2024 and provide evidence to support a PVS strategy. A four-pronged, targeted, cross-sectional study was conducted in the Tongan districts of Tongatapu, Ha’apai, and Ongo Niuas in May–July 2024 in communities, primary schools, high schools, and an outpatient clinic. Participants were tested for LF antigen (Ag) and microfilariae (Mf). The outcome measure for persistent LF transmission was Ag-positivity. Between 9 May and 19 July 2024, 1787 participants were recruited from 12 communities, 11 primary schools, five high schools, and one outpatient clinic. Overall, 39 participants (2·2%) were Ag-positive and five (0·3%) were Mf-positive. The highest Ag prevalence was in communities (4·0%; 95% confidence interval [95%CI]: 2·9–5·6), where all Mf-positives (n = 5) were identified. Ag-positivity was associated with male sex (adjusted odds ratio [aOR]:4·86; 95%CI: 2·25–10·46), older age (>50 years vs 5–10 years [aOR:7·51; 95%CI: 2·13–26·47]), and residing in Ha’apai (aOR:15·08; 95%CI: 5·41–42·05) and Ongo Niuas (aOR:10·85; 95%CI: 3·91–30·08). We found persistent LF transmission in Tonga seven years post-validation. Community surveillance yielded the highest Ag and Mf prevalence. Efficiency of PVS could be improved by integrating surveillance activities into the existing health system and conducting community-based surveys, particularly among older males and in high prevalence areas. Task Force for Global Health, 10.13039/100000865 Bill & Melinda Gates Foundation , and the 10.13039/100000200 United States Agency for International Development .

Spatial variation in drivers of leptospirosis transmission in the Dominican Republic is poorly understood. To inform targeted public health interventions, we aimed to characterise risk factors and drivers of transmission on a fine spatial scale. We analysed data from 2078 participants in two provinces, Espaillat and San Pedro de Macoris (SPM), collected from a 2021 cross-sectional survey. We used geographically weighted regression to quantify associations between leptospirosis seropositivity and spatial environmental and sociodemographic data. In Espaillat, higher odds of seropositivity were associated with exposure to freshwater (OR 6.51, ranging between 5.95 and 6.99), bare ground coverage above 1.44% (OR 3.70;3.49–3.92), river density surrounding the household at the highest quartile (OR 2.43;2.41–2.45) and average precipitation in the last five years at the highest quartile (2.57; 2.52–2.65). In SPM, rat exposure was associated with higher odds of seropositivity (OR 2.59;1.23–3.14). By identifying locally important drivers of transmission, our study provides evidence to support more tailored public health interventions to optimise the control and prevention of leptospirosis.

Incidence of COVID-19 has been associated with sociodemographic factors. We investigated variations in SARS-CoV-2 seroprevalence at sub-national levels in the Dominican Republic and assessed potential factors influencing variation in regional-level seroprevalence. Data were collected in a three-stage cross-sectional national serosurvey from June to October 2021. Seroprevalence of antibodies against the SARS-CoV-2 spike protein (anti-S) was estimated and adjusted for selection probability, age, and sex. Multilevel logistic regression was used to estimate the effect of covariates on seropositivity for anti-S and correlates of 80% protection (PT₈₀) against symptomatic infection for the ancestral and Delta strains. A total of 6683 participants from 134 clusters in all 10 regions were enrolled. Anti-S, PT80 for the ancestral and Delta strains odds ratio varied across regions, Enriquillo presented significant higher odds for all outcomes compared with Yuma. Compared to being unvaccinated, receiving ≥2 doses of COVID-19 vaccine was associated with a significantly higher odds of anti-S positivity (OR 85.94, [10.95–674.33]) and PT₈₀ for the ancestral (OR 4.78, [2.15–10.62]) and Delta strains (OR 3.08, [1.57–9.65]) nationally and also for each region. Our results can help inform regional-level public health response, such as strategies to increase vaccination coverage in areas with low population immunity against currently circulating strains.

Contrasting evidence is emerging on the long-term effectiveness of triple-drug therapy for elimination of lymphatic filariasis (LF) in the Pacific region. We evaluated the effectiveness of ivermectin, diethylcarbamazine and albendazole (IDA) for sustained clearance of microfilariae (Mf) in Samoa. We enrolled two cohorts of Mf-positive participants. Cohort A were Mf-positive participants from 2018, who received directly observed triple-drug therapy in 2019 and were retested and retreated in 2023 and 2024. Cohort B were Mf-positive and treated in 2023 and retested in 2024. Participants were tested for LF antigen and Mf. In Cohort A, eight of the 14 participants from 2018/2019 were recruited in 2023; six were Mf-positive. In 2024, six participants were retested, and two were Mf-positive. Cohort B included eight participants, and two remained Mf-positive in 2024. Mf prevalence in 2023 for Cohort A (71.4%, 95% CI 29.0%-96.3%) was significantly higher than among their household members (12.0%, 95% CI 2.5%-31.2%). One or two doses of directly observed IDA was not sufficient for sustained clearance of Wuchereria bancrofti Mf in Samoa. The high Mf prevalence in treated individuals compared to household members suggests recrudescence rather than reinfection.

Background: In recent decades, spatial epidemiology has increasingly been used to study neglected tropical diseases (NTDs). Spatial methods are particularly relevant when transmission is strongly driven by sociodemographic and environmental factors, resulting in heterogeneous disease distribution. We use lymphatic filariasis (LF)—an NTD targeted for global elimination—as a case study to examine how spatial epidemiology has been used to enhance NTD surveillance. Methods: We conducted a systematic literature review of spatial analytical studies of LF published in English across PubMed, Embase, Web of Science and Scopus databases, before 15 November 2022. Additional papers were identified from experts’ suggestions. Studies that employed spatial analytical methods were included, but those that applied only visualisation tools were excluded. Findings: Sixty-one eligible studies published between 1997 and 2023 were identified. The studies used a wide range of spatial methods. Thirty-one (50.8%) studies used spatial statistical modelling, with model-based geostatistics being the most common method. Spatial autocorrelation and hotspot analysis were applied in 30 studies (49.2%). The most frequent model outputs were prevalence maps (17 studies, 27.9%), followed by risk maps based on environmental suitability (7 studies, 11.5%) and maps of the odds of seroprevalence being above a predetermined threshold (7 studies, 11.5%). Interpretation: By demonstrating the applicability of spatial methods for investigating transmission drivers, identifying clusters and predicting hotspots, we highlight innovative ways in which spatial epidemiology has provided valuable evidence to support LF elimination. Spatial analysis is particularly useful in low-prevalence settings for improving hotspot detection and enhancing postelimination surveillance. PROSPERO registration number: CRD42022333804.