Mathematical models within the Ross-Macdonald framework increasingly play a role in our understanding of vector-borne disease dynamics and as tools for assessing scenarios to respond to emerging threats. These threats are typically characterized by a high degree of heterogeneity, introducing a range of possible complexities in models and challenges to maintain the link with empirical evidence. We systematically identified and analysed a total of 77 published papers presenting compartmental West Nile virus (WNV) models that use parameter values derived from empirical studies. Using a set of 15 criteria, we measured the dissimilarity compared with the Ross-Macdonald framework. We also retrieved the purpose and type of models and traced the empirical sources of their parameters. Our review highlights the increasing refinements in WNV models. Models for prediction included the highest number of refinements. We found uneven distributions of refinements and of evidence for parameter values. We identified several challenges in parametrizing such increasingly complex models. For parameters common to most models, we also synthesize the empirical evidence for their values and ranges. The study highlights the potential to improve the quality of WNV models and their applicability for policy by establishing closer collaboration between mathematical modelling and empirical work.

Background In recent years the Asian bush mosquito Aedes japonicus has invaded Europe, including the Netherlands. This species is a known vector for a range of arboviruses, possibly including West Nile virus (WNV). As WNV emerged in the Netherlands in 2020, it is important to investigate the vectorial capacity of mosquito species present in the Netherlands to estimate the risk of future outbreaks and further spread of the virus. Therefore, this study evaluates the potential role of Ae. japonicus in WNV transmission and spillover from birds to dead-end hosts in the Netherlands. Methods We conducted human landing collections in allotment gardens (Lelystad, the Netherlands) in June, August and September 2021 to study the diurnal and seasonal host-seeking behaviour of Ae. japonicus. Furthermore, their host preference in relation to birds using live chicken-baited traps was investigated. Vector competence of field-collected Ae. japonicus mosquitoes for two isolates of WNV at two different temperatures was determined. Based on the data generated from these studies, we developed a Susceptible-Exposed-Infectious-Recovered (SEIR) model to calculate the risk of WNV spillover from birds to humans via Ae. japonicus, under the condition that the virus is introduced and circulates in an enzootic cycle in a given area. Results Our results show that Ae. japonicus mosquitoes are actively host seeking throughout the day, with peaks in activity in the morning and evening. Their abundance in August was higher than in June and September. For the host-preference experiment, we documented a small number of mosquitoes feeding on birds: only six blood-fed females were caught over 4 full days of sampling. Finally, our vector competence experiments with Ae. japonicus compared to its natural vector Culex pipiens showed a higher infection and transmission rate when infected with a local, Dutch, WNV isolate compared to a Greek isolate of the virus. Interestingly, we also found a small number of infected Cx. pipiens males with virus-positive leg and saliva samples. Conclusions Combining the field and laboratory derived data, our model predicts that Ae. japonicus could act as a spillover vector for WNV and could be responsible for a high initial invasion risk of WNV when present in large numbers.

Background The global mining industry is an important partner in advancing the 2030 Agenda for Sustainable Development. In 2018, Anglo American plc published their Sustainable Mining Plan, containing a goal for improving health and wellbeing aligned with the Sustainable Development Goal 3 (SDG3) targets. Having formed an independent multidisciplinary research consortium, we designed and implemented a mixed-methods approach to attain a deeper understanding of SDG3 priorities within the local context of communities hosting Anglo American mining operations located in Latin America. Methods In 2019, within the host communities of three mining operations in Chile, three in Brazil, and one in Peru, we conducted a qualitative study which included stakeholder workshops and key informant interviews. We also quantitatively appraised existing health data. Findings emerging from the qualitative and quantitative assessments were compared to identify health and wellbeing priority areas for action relevant to each community. Results Across the three countries, 120 people took part in workshops and 35 in interviews. In these workshops and interviews, non-communicable diseases (SDG3.4), harmful alcohol consumption (SDG3.5), and pollution, particularly air pollution (SDG3.9), were consistently identified as areas for priority action. There were similarities in the reporting of individual, interpersonal, community, societal, and structural factors underlying these priority areas across the different communities . The availability of quantitative data was generally good at the state level, becoming increasing sparse as we focused on smaller geographies. The priorities identified in the quantitative assessments generally aligned with those highlighted in the qualitative data. Conclusions We highlight the importance of engaging with local populations to understand and address health needs. To address the priorities identified, intervention packages tailored to the specific needs of host communities, that tackle associated upstream societal level factors, are required. To facilitate this, appropriate monitoring systems and epidemiological investigations should be implemented to better understand the local context and quantify health issues. In the host communities, it is essential for the mining sector to be a key health partner in promoting integrated programmes that contribute to achieving the priority objectives and targets aligned with the SDG3 agenda.

Quantifying the variation of pathogens' life history traits in multiple host systems is crucial to understand their transmission dynamics. It is particularly important for arthropod-borne viruses (arboviruses), which are prone to infecting several species of vertebrate hosts. Here, we focus on how host-pathogen interactions determine the ability of host species to transmit a virus to susceptible vectors upon a potentially infectious contact. Rift Valley fever (RVF) is a viral, vector-borne, zoonotic disease, chosen as a case study. The relative contributions of livestock species to RVFV transmission has not been previously quantified. To estimate their potential to transmit the virus over the course of their infection, we 1) fitted a within-host model to viral RNA and infectious virus measures, obtained daily from infected lambs, calves, and young goats, 2) estimated the relationship between vertebrate host infectious titers and probability to infect mosquitoes, and 3) estimated the net infectiousness of each host species over the duration of their infectious periods, taking into account different survival outcomes for lambs. Our results indicate that the efficiency of viral replication, along with the lifespan of infectious particles, could be sources of heterogeneity between hosts. Given available data on RVFV competent vectors, we found that, for similar infectious titers, infection rates in the Aedes genus were on average higher than in the Culex genus. Consequently, for Aedes-mediated infections, we estimated the net infectiousness of lambs to be 2.93 (median) and 3.65 times higher than that of calves and goats, respectively. In lambs, we estimated the overall infectiousness to be 1.93 times higher in individuals which eventually died from the infection than in those recovering. Beyond infectiousness, the relative contributions of host species to transmission depend on local ecological factors, including relative abundances and vector host-feeding preferences. Quantifying these contributions will ultimately help design efficient, targeted, surveillance and vaccination strategies.

Objectives: To estimate HIV incidence among female sex workers (FSW) in Zimbabwe: using HIV prevalence by age and number of years since started selling sex (YSSS). Design: We pooled data from FSW aged 18–39 participating in respondent-driven sampling surveys conducted in Zimbabwe between 2011 and 2017. Methods: For each year of age, we estimated: HIV prevalence ( P t ) and the change in HIV prevalence from the previous age ( P t − P t−1 ). We then estimated the rate of new HIV infections during that year of age: I t = P t − P t−1 /(1 − P t−1 ), and calculated HIV incidence for 18–24 and 25–39 year-olds separately as the weighted average of I t . We estimated HIV incidence for FSW 1–5 years and 6–15 years since first selling sex using the same approach, and compared HIV prevalence among FSW first selling sex at their current age with the general population. Results: Among 9906 women, 50.2% were HIV positive. Based on HIV prevalence increases by age, we estimated an HIV incidence of 6.3/100 person-years at risk (pyar) (95% confidence interval [CI] 5.3, 7.6) among 18–24 year-olds, and 3.3/100 pyar (95% CI 1.3, 4.2) among 25–39 year-olds. Based on prevalence increases by YSSS, HIV incidence was 5.3/100 pyar (95% CI 4.3, 8.5) between 1 and 5 years since first selling sex, and 2.1/100 pyar (95% CI −1.3, 7.2) between 6 and 15 years. Conclusions: Our analysis is consistent with very high HIV incidence among FSW in Zimbabwe, especially among those who are young and recently started selling sex. There is a critical need to engage young entrants into sex work in interventions that reduce their HIV risk.

Background: To reduce HIV incidence among adolescent girls who sell sex (AGSS) in Zimbabwe, we need to better understand how vulnerabilities intersect with HIV infection and how those living with HIV engage in care. Methods: In 2017, we conducted social mapping in 4 locations in Zimbabwe and recruited girls aged 16-19 years who sell sex, using respondent-driven sampling or census sampling methods. Participants completed a questionnaire and provided finger prick blood samples for HIV antibody testing. Results: Of 605 AGSS recruited, 74.4% considered themselves sex workers, 24.4% reported experiencing violence in the past year, 91.7% were not in school, and 83.8% had less than a complete secondary education. Prevalence of HIV increased steeply from 2.1% among those aged 16 years to 26.9% among those aged 19 years; overall, 20.2% of AGSS were HIV-positive. In the multivariate analysis, age, education, marital status, and violence from a client were associated with HIV. Among the 605 AGSS, 86.3% had ever tested for HIV, with 64.1% having tested in the past 6 months. Among AGSS living with HIV, half (50.8%) were aware of their status, among whom 83.9% reported taking antiretroviral therapy. Conclusion: The steep rise in HIV prevalence among those aged between 16 and 19 years suggests the window to engage with AGSS before HIV acquisition is short. To accelerate reductions in incidence among AGSS, intensified combination prevention strategies that address structural factors and tailor services to the needs of AGSS are required, particularly ensuring girls enroll and remain in school.

Background The global mining industry has an opportunity to mobilize resources to advance progress against the Sustainable Development Goals (SDGs). In 2018, the Anglo-American Group outlined aspirations for mining host communities to meet the SDG3 health targets. To progress from aspiration to action we designed and implemented a mixed-methods approach to attain a deeper understanding of the health and wellbeing priorities within the local context of host communities of fifteen mines in South Africa. Methods To identify local needs and priorities relating to SDG3 targets in host communities, stakeholder workshops and key informant interviews were conducted between June and August 2019. A baseline assessment of health data, related to each of the SDG3 targets and indicators and to each host community location, was also conducted. Findings emerging from the qualitative and quantitative baseline assessments were compared to identify the extent to which health issues aligned and health and wellbeing priority areas for action. Results A total of 407 people participated in the workshops, and 85 key informants were interviewed. Quantitative data were available at sub-national level for seven of the nine SDG3 targets and eleven of the 21 indicators. Key priority areas for action identified through alignment of the qualitative and quantitative data were maternal mortality (SDG3.1), HIV (SDG3.3.1), tuberculosis (SDG3.3.2), substance abuse (SDG3.5), and road traffic accidents (SDG3.6) We found consistency in the individual, interpersonal, community, societal, and structural factors underlying these priority areas. At a structural level, poor access to quality healthcare was raised at every workshop as a key factor underlying the achievement of all SDG3 targets. Of the five priority areas identified, HIV, TB and substance abuse were found to overlap in the study communities in terms of risk, burden, and underlying factors. Conclusions We demonstrate a mixed method approach for identifying local health needs and prioritised SDG3 targets in mining host communities. Consistency in reporting suggests the need for effective, efficient and feasible interventions to address five priority areas. Given the prominent economic role of the mining sector in South Africa, it can play a critical role in implementing programmatic activities that further progress towards achieving the SDG3 targets.

Abstract Background Malaria and malnutrition remain major problems in Sahel countries, especially in young children. The direct effect of malnutrition on malaria remains poorly understood, and may have important implications for malaria control. In this study, nutritional status and the association between malnutrition and subsequent incidence of symptomatic malaria were examined in children in Burkina Faso and Mali who received either azithromycin or placebo, alongside seasonal malaria chemoprevention. Methods Mid-upper arm circumference (MUAC) was measured in all 20,185 children who attended a screening visit prior to the malaria transmission season in 2015. Prior to the 2016 malaria season, weight, height and MUAC were measured among 4149 randomly selected children. Height-for-age, weight-for-age, weight-for-height, and MUAC-for-age were calculated as indicators of nutritional status. Malaria incidence was measured during the following rainy seasons. Multivariable random effects Poisson models were created for each nutritional indicator to study the effect of malnutrition on clinical malaria incidence for each country. Results In both 2015 and 2016, nutritional status prior to the malaria season was poor. The most prevalent form of malnutrition in Burkina Faso was being underweight (30.5%; 95% CI 28.6–32.6), whereas in Mali stunting was most prevalent (27.5%; 95% CI 25.6–29.5). In 2016, clinical malaria incidence was 675 per 1000 person-years (95% CI 613–744) in Burkina Faso, and 1245 per 1000 person-years (95% CI 1152–1347) in Mali. There was some evidence that severe stunting was associated with lower incidence of malaria in Mali (RR 0.81; 95% CI 0.64–1.02; p = 0.08), but this association was not seen in Burkina Faso. Being moderately underweight tended to be associated with higher incidence of clinical malaria in Burkina Faso (RR 1.27; 95% CI 0.98–1.64; p = 0.07), while this was the case in Mali for moderate wasting (RR 1.27; 95% CI 0.98–1.64; p = 0.07). However, these associations were not observed in severely affected children, nor consistent between countries. MUAC-for-age was not associated with malaria risk. Conclusions Both malnutrition and malaria were common in the study areas, high despite high coverage of seasonal malaria chemoprevention and long-lasting insecticidal nets. However, no strong or consistent evidence was found for an association between any of the nutritional indicators and the subsequent incidence of clinical malaria.

Introduction Testing for recent HIV infection can distinguish recently acquired infection from long-standing infections. Given current interest in the implementation of recent infection testing algorithms (RITA), we report our experiences in implementing a RITA in three pilot studies and highlight important issues to consider when conducting recency testing in routine settings. Methods We applied a RITA, incorporating a limited antigen (LAg) avidity assay, in different routine HIV service-delivery settings in 2018: antenatal care clinics in Siaya County, Kenya, HIV testing and counselling facilities in Nairobi, Kenya, and female sex workers clinics in Zimbabwe. Discussions were conducted with study coordinators, laboratory leads, and facility-based stakeholders to evaluate experiences and lessons learned in relation to implementing recency testing. Results In Siaya County 10/426 (2.3%) of women testing HIV positive were classified as recent, compared to 46/530 (8.7%) of women and men in Nairobi and 33/313 (10.5%) of female sex workers in Zimbabwe. Across the study setting, we observed differences in acceptance, transport and storage of dried blood spot (DBS) or venous blood samples. For example, the acceptance rate when testing venous blood was 11% lower than when using DBS. Integrating our study into existing services ensured a quick start of the study and kept the amount of additional resources required low. From a laboratory perspective, the LAg avidity assay was initially difficult to operationalise, but developing a network of laboratories and experts to work together helped to improve this. A challenge that was not overcome was the returning of RITA test results to clients. This was due to delays in laboratory testing, the need for multiple test results to satisfy the RITA, difficulties in aligning clinic visits, and participants opting not to return for test results. Conclusion We completed three pilot studies using HIV recency testing based on a RITA in Kenya and Zimbabwe. The main lessons we learned were related to sample collection and handling, LAg avidity assay performance, integration into existing services and returning of test results to participants. Our real-world experience could provide helpful guidance to people currently working on the implementation of HIV recency testing in sub-Saharan Africa.

Introduction Surveillance of recent HIV infections in national testing services has the potential to inform primary prevention programming activities. Focusing on procedures required to accurately determine recent infection, and the potential for recent infection surveillance to inform prevention efforts, we present the results of three independent but linked pilots of recency testing. Methods To distinguish recently acquired HIV infection from long-standing infection, in 2018 we applied a Recent Infection Testing Algorithm that combined a laboratory-based Limiting Antigen Avidity Enzyme Immunoassay with clinical information (viral-load; history of prior HIV diagnosis; antiretroviral therapy-exposure). We explored potential misclassification of test results and analysed the characteristics of participants with recent infection. We applied the algorithm in antenatal clinics providing prevention of mother-to-child transmission services in Siaya County, Kenya, outreach sites serving female sex workers in Zimbabwe, and routine HIV testing and counselling facilities in Nairobi, Kenya. In Nairobi, we also conducted recency testing among partners of HIV-positive participants. Results In Siaya County, 2.3% (10/426) of HIV-positive pregnant women were classified as recent. A risk factor analysis comparing women testing recent with those testing HIV-negative found women in their first trimester were significantly more likely to test recent than those in their second or third trimester. In Zimbabwe, 10.5% (33/313) of female sex workers testing HIV-positive through the outreach programme were classified recent. A risk factor analysis of women testing recent versus those testing HIV-negative, found no strong evidence of an association with recent infection. In Nairobi, among 532 HIV-positive women and men, 8.6% (46) were classified recent. Among partners of participants, almost a quarter of those who tested HIV-positive were classified as recent (23.8%; 5/21). In all three settings, the inclusion of clinical information helped improve the positive predictive value of recent infection testing by removing cases that were likely misclassified. Conclusions We successfully identified recently acquired infections among persons testing HIV-positive in routine testing settings and highlight the importance of incorporating additional information to accurately classify recent infection. We identified a number of groups with a significantly higher proportion of recent infection, suggesting recent infection surveillance, when rolled-out nationally, may help in further targeting primary prevention efforts.

Background: Serological tests can distinguish recent (in the prior 12 months) from long-term HIV infection. Integrating recency testing into routine HIV testing services (HTS) can provide important information on transmission clusters and prioritize clients for partner testing. This study assessed the feasibility and use of integrating HIV recency into routine testing. Methods: We conducted a multi-method study at 14 facilities in Kenya, and key informant interviews with health care providers. We abstracted clinical record data, collected specimens, tested specimens for recent infection, returned results to participants, and conducted a follow-up survey for those recently infected. Results: From March to October 2018, we enrolled 532 clients who were diagnosed HIV-positive for the first time. Of these, 46 (8.6%) were recently infected. Women aged 15–24 years had 2.9 (95% confidence interval: 1.46 to 5.78) times higher adjusted odds of recent infection compared with 15–24-year-old men and those tested within the past 12 months having 2.55 (95% confidence interval: 0.38 to 4.70) times higher adjusted odds compared with those tested ≥12 months previously. Fourteen of 17 providers interviewed found the integration of recency testing into routine HTS services acceptable and feasible. Among clients who completed the follow-up interview, most (92%) felt that the recency results were useful. Conclusions: Integrating recent infection testing into routine HTS services in Kenya is feasible and largely acceptable to clients and providers. More studies should be done on possible physical and social harms related to returning results, and the best uses of the recent infection data at an individual and population level.

Background: In Tanzania, HIV testing data are reported aggregately for national surveillance, making it difficult to accurately measure the extent to which newly diagnosed persons are entering care, which is a critical step of the HIV care cascade. We assess, at the individual level, linkage of newly diagnosed persons to HIV care. Methods: An expanded two-part referral form was developed to include additional variables and unique identifiers. The expanded form contained a corresponding number for matching the two-parts between testing and care. Data were prospectively collected at 16 health facilities in the Magu District of Tanzania. Results: The records of 1,275 unique people testing HIV positive were identified and included in our analysis. Of these, 1,200 (94.1%) responded on previous testing history, with 184 (15.3%) testing twice or more during the pilot, or having had a previous HIV positive test. Three-quarters (932; 73.1%) of persons were linked to care during the pilot timeframe. Health service provision in the facility carrying out the HIV test was the most important factor for linkage to care; poor linkage occurred in facilities where HIV care was not immediately available. Conclusions: It is critical for persons newly diagnosed with HIV to be linked to care in a timely manner to maximize treatment effectiveness. Our findings show it is feasible to measure linkage to care using routinely collected data arising from an amended national HIV referral form. Our results illustrate the importance of utilizing individual-level data for measuring linkage to care, as repeat testing is common.