Zika transmission patterns: a meta-review.

OBJECTIVE: To assesses what is known and identify knowledge gaps for Zika virus (ZIKV) transmission patterns. METHODS: Meta-review searching the databases BioSys; Cochrane Infectious Diseases Group Specialised Register and Cochrane Central Register of Controlled Trials; EMBASE; Google Scholar; LILACS; MEDLINE (PubMed); Web of Science; and WHOLIS with the term 'ZIKA'. Systematic reviews and reviews specifying the search methods and describing potential modes of transmission were eligible for analysis. RESULTS: Of 5,401 hits for 'Zika', 44 studies were assessed and 11 included after applying in- and exclusion criteria: six systematic reviews and five reviews with specified methods, covering all ways of possible transmission. Results can be grouped into transmission routes with good evidence and agreement between the studies (evidence on vector, mother-to-child and sexual transmission) and transmission routes with limited evidence. Transmission by breastfeeding, intrapartum, by animal bites or laboratory-based remains inconclusive, as these routes are suggested by single studies only. The risk of transfusion transmission is described and public health measures for safe transfusion should be taken as available. CONCLUSION: Our results imply the need for public health measures to limit transmission via vectors, mother-to-child, sexual transmission and blood transfusion. Also needed are long-term prospective cohort studies covering periods of active Zika virus transmission and measuring epidemiological parameters to establish evidence on other routes of transmission; seroprevalence studies; transmission dynamics modelling and modelling health impacts by different modes of transmission.

OBJECTIF: Evaluer ce que l'on sait et identifier les lacunes dans les connaissances sur les profils de transmission du virus Zika (ZIKV). MÉTHODES: Méta-analyse de recherche dans les bases de données BioSys, Cochrane Infectious Diseases Specialised Register et le Registre Central Cochrane des Essais Contrôlés, EMBASE, Google Scholar, LILACS MEDLINE (PubMed), Web de la Science et WHOLIS avec le terme «Zika¼. Les revues systématiques et les revues spécifiant les méthodes de recherche et décrivant les modes de transmission potentiels étaient éligibles pour l'analyse. RÉSULTATS: Sur 5.401 résultats correspondant à «Zika¼, 44 études ont été évaluées et 11 incluses après application des critères d'inclusion et d'exclusion: 6 revues systématiques et 5 revues avec des méthodes spécifiées, couvrant tous les modes de transmission possibles. Les résultats peuvent être regroupés en voies de transmission avec des preuves solides et une concordance entre les études (preuves sur la transmission vectorielle, transmission mère-enfant et sexuelle) et les voies de transmission avec des preuves limitées. La transmission par l'allaitement, par voie intra-partum, par des morsures d'animaux ou via le laboratoire reste non conclusive, car ces voies ne sont suggérées que par des études uniques. Le risque de transmission par transfusion est décrit et des mesures de santé publique visant à garantir une transfusion sans danger doivent être prises dès que possible. CONCLUSION: Nos résultats insinuent la nécessité de prendre des mesures de santé publique pour limiter la transmission par le biais des vecteurs, la transmission mère-enfant, la transmission sexuelle et la transfusion sanguine. Des études de cohorte prospectives à long terme portant sur des périodes de transmission active du virus Zika et des mesures de paramètres épidémiologiques sont également nécessaires pour établir des preuves d'autres voies de transmission; des études de séroprévalence; la modélisation de la dynamique de transmission et la modélisation des impacts sur la santé par différents modes de transmission.

Efficacy and community effectiveness of larvivorous fish for dengue vector control.

OBJECTIVE: To evaluate the efficacy and community effectiveness of larvivorous fish for the control of dengue vectors and dengue transmission, when used as a single agent or in combination with other vector control methods. METHOD: Comprehensive literature search of published and grey literature using PubMed, EMBASE (DMDI), Web of Science, WHOLIS, WILEY, LILACS, GIFT, Cochrane Library, ELDIS, New York Academy of Medicine Grey Literature Report and Google. All results were checked for duplicates and examined for eligibility. Methodological quality of the studies was assessed using RoBANS. RESULTS: Thirteen articles were considered eligible for inclusion. Incorporating a wide range of interventions and outcome measures, three were efficacy studies and 10 assessed community effectiveness. None of the studies were randomised or cluster-randomised controlled trials. All three efficacy studies and seven community effectiveness studies investigated fish as a single agent. All efficacy studies reported elimination of Aedes larvae from treated containers, while community effectiveness studies reported reductions in immature vector stages, two of which also detected a continuous decline over 2 years. An impact on adult mosquitoes was shown in only two community effectiveness studies. Reductions in dengue cases following intervention were reported in two studies, but it was not possible to attribute this to the intervention. CONCLUSION: While the use of larvivorous fish as a single agent or in combination with other control measures could lead to reductions in immature vector stages, considerable limitations in all the studies restricted any conclusions with respect to the evaluation of community effectiveness. Evidence for the community effectiveness of larvivorous fish as a single agent remains minimal and cluster-randomised controlled studies that include the assessment of impact on dengue are recommended.

Community effectiveness of copepods for dengue vector control: systematic review.

OBJECTIVE: Vector control remains the only available method for primary prevention of dengue. Several interventions exist for dengue vector control, with limited evidence of their efficacy and community effectiveness. This systematic review compiles and analyses the existing global evidence for community effectiveness of copepods for dengue vector control. METHODS: The systematic review follows the PRISMA statement, searching six relevant databases. Applying all inclusion and exclusion criteria, 11 articles were included. RESULTS: There is evidence that cyclopoid copepods (Mesocyclops spp.) could potentially be an effective vector control option, as shown in five community effectiveness studies in Vietnam. This includes long-term effectiveness for larval and adult control of Ae. aegypti, as well as dengue incidence. However, this success has so far not been replicated elsewhere (six studies, three community effectiveness studies--Costa Rica, Mexico and USA, and three studies analysing both efficacy and community effectiveness--Honduras, Laos and USA), probably due to community participation, environmental and/or biological factors. Judging by the quality of existing studies, there is a lack of good study design, data quality and appropriate statistics. CONCLUSION: There is limited evidence for the use of cyclopoid copepods as a single intervention. There are very few studies, and more are needed in other communities and environments. Clear best practice guidelines for the methodology of entomological studies should be developed.

Dengue disease surveillance: an updated systematic literature review.

OBJECTIVES: To review the evidence for the application of tools for dengue outbreak prediction/detection and trend monitoring in passive and active disease surveillance systems in order to develop recommendations for endemic countries and identify important research needs. METHODS: This systematic literature review followed the protocol of a review from 2008, extending the systematic search from January 2007 to February 2013 on PubMed, EMBASE, CDSR, WHOLIS and Lilacs. Data reporting followed the PRISMA statement. The eligibility criteria comprised (i) population at risk of dengue, (ii) dengue disease surveillance, (iii) outcome of surveillance described and (iv) empirical data evaluated. The analysis classified studies based on the purpose of the surveillance programme. The main limitation of the review was expected publication bias. RESULTS: A total of 1116 papers were identified of which 36 articles were included in the review. Four cohort-based prospective studies calculated expansion factors demonstrating remarkable levels of underreporting in the surveillance systems. Several studies demonstrated that enhancement methods such as laboratory support, sentinel-based reporting and staff motivation contributed to improvements in dengue reporting. Additional improvements for passive surveillance systems are possible by incorporating simple data forms/entry/electronic-based reporting; defining clear system objectives; performing data analysis at the lowest possible level (e.g. district); seeking regular data feedback. Six studies showed that serotype changes were positively correlated with the number of reported cases or with dengue incidence, with lag times of up to 6 months. Three studies found that data on internet searches and event-based surveillance correlated well with the epidemic curve derived from surveillance data. CONCLUSIONS: Passive surveillance providing the baseline for outbreak alert should be strengthened and appropriate threshold levels for outbreak alerts investigated. Additional enhancement tools such as syndromic surveillance, laboratory support and motivation strategies can be added. Appropriate alert signals need to be identified and integrated into a risk assessment tool. Shifts in dengue serotypes/genotype or electronic event-based surveillance have also considerable potential as indicator in dengue surveillance. Further research on evidence-based response strategies and cost-effectiveness is needed.