The decline of dengue in the Americas in 2017: discussion of multiple hypotheses.

OBJECTIVE: Since the 1980s, dengue incidence has increased 30-fold. However, in 2017, there was a noticeable reduction in reported dengue incidence cases within the Americas, including severe and fatal cases. Understanding the mechanism underlying dengue's incidence and decline in the Americas is vital for public health planning. We aimed to provide plausible explanations for the decline in 2017. METHODS: An expert panel of representatives from scientific and academic institutions, Ministry of Health officials from Latin America and PAHO/WHO staff met in October 2017 to propose hypotheses. The meeting employed six moderated plenary discussions in which participants reviewed epidemiological evidence, suggested explanatory hypotheses, offered their expert opinions on each and developed a consensus. RESULTS: The expert group established that in 2017, there was a generalised decreased incidence, severity and number of deaths due to dengue in the Americas, accompanied by a reduction in reported cases of both Zika and chikungunya virus infections, with no change in distribution among age groups affected. This decline was determined to be unlikely due to changes in epidemiological surveillance systems, as similar designs of surveillance systems exist across the region. Although sudden surveillance disruption is possible at a country or regional level, it is unlikely to occur in all countries simultaneously. Retrospective modelling with epidemiological, immunological and entomological information is needed. Host or immunological factors may have influenced the decline in dengue cases at the population level through immunity; however, herd protection requires additional evidence. Uncertainty remains regarding the effect on the outcome of sequential infections of different dengue virus (DENV) types and Zika virus (ZIKV), and vice versa. Future studies were recommended that examine the epidemiological effect of prior DENV infection on Zika incidence and severity, the epidemiological effect of prior Zika virus infection on dengue incidence and severity, immune correlates based on new-generation ELISA assays, and impact of prior DENV/other arbovirus infection on ZIKV immune response in relation to number of infections and the duration of antibodies in relation to interval of protection. Follow-up studies should also investigate whether increased vector control intensification activities contributed to the decline in transmission of one or more of these arboviruses. Additionally, proposed studies should focus on the potential role of vector competence when simultaneously exposed to various arboviruses, and on entomological surveillance and its impact on circulating vector species, with a goal of applying specific measures that mitigate seasonal occurrence or outbreaks. CONCLUSIONS: Multifactorial events may have accounted for the decline in dengue seen in 2017. Differing elements might explain the reduction in dengue including elements of immunity, increased vector control, and even vector and\or viruses changes or adaptations. Most of the results of this expert consensus group meeting are hypothetical and based on limited evidence. Further studies are needed.

OBJECTIF: Depuis les années 1980, l'incidence de la dengue a été multipliée par 30. Cependant, en 2017, il y a eu une réduction notable du nombre de cas d'incidence de dengue rapportés dans les Amériques. Nous voulions fournir des explications plausibles à la baisse en 2017. MÉTHODES: Un groupe d'experts constitué de représentants d'institutions scientifiques et académiques, d'officiels des Ministères de la Santé d'Amérique Latine et de membres du personnel de l'OPS/OMS s'est réuni en octobre 2017 pour proposer et évaluer des hypothèses. RÉSULTATS: En 2017, il y a eu une baisse généralisée de l'incidence, de la sévérité et du nombre de décès dus à la dengue dans les Amériques, accompagnée d'une réduction des cas rapportés d'infections par le virus Zika et par le virus du chikungunya, sans modification dans la répartition entre les groupes d'âge affectés. Il a été déterminé que ce déclin était peu probablement dû aux changements dans les systèmes de surveillance épidémiologique, étant donné que des systèmes de surveillance similaires existaient dans toute la région. Bien que des perturbations soudaines dans la surveillance soient possibles au niveau national ou régional, il est peu probable que cela se produise simultanément dans tous les pays. Une modélisation rétrospective avec des informations épidémiologiques, immunologiques et entomologiques est nécessaire. Des facteurs liés à l'hôte ou immunologiques peuvent avoir influencé le déclin des cas de dengue au niveau de la population par le biais de l'immunité; cependant, l'évidence d'une protection conférée par l'effet du troupeau nécessite des données supplémentaires. Une incertitude subsiste quant à l'effet sur le résultat des infections séquentielles de différents types du virus de la dengue (DENV) et du virus Zika (ZIKV), et vice-versa. Les études à venir devraient examiner (1) l'effet épidémiologique d'une infection antérieure par le DENV sur l'incidence et la sévérité du virus Zika, (2) l'effet épidémiologique d'une infection antérieure par le virus Zika sur l'incidence et la sévérité de la dengue, (3) les corrélats immunitaires basés sur des tests ELISA de nouvelle génération, (4) l' impact d'une infection antérieure à DENV/autres arbovirus sur la réponse immunitaire au ZIKV en fonction du nombre d'infections et de la durée des anticorps en fonction de l'intervalle de protection, (5) si des activités d'intensification de la lutte antivectorielle ont contribué à la diminution de la transmission d'un ou plusieurs de ces arbovirus, (6) le rôle potentiel de la compétence vectorielle lorsqu'ils sont exposés simultanément à différents arbovirus, (7) la surveillance entomologique et son impact sur la circulation d'espèces de vecteurs, dans le but d'appliquer des mesures spécifiques qui réduisent l'occurrence saisonnière d'épidémies. CONCLUSIONS: Des événements multifactoriels pourraient expliquer le déclin observé de la dengue en 2017. La plupart des résultats de cette réunion du groupe de consensus d'experts sont hypothétiques, reposent sur des données limitées et requièrent des investigations supplémentaires.

Schistosomiasis Prevalence and Intensity of Infection in Latin America and the Caribbean Countries, 1942-2014: A Systematic Review in the Context of a Regional Elimination Goal.

BACKGROUND: In 2012 the World Health Assembly adopted resolution WHA65.21 on elimination of schistosomiasis, calling for increased investment in schistosomiasis control and support for countries to initiate elimination programs. This study aims to analyze prevalence and intensity of Schistosoma mansoni infection in children in Latin America and the Caribbean countries and territories (LAC), at the second administrative level or lower. METHODOLOGY: A systematic review of schistosomiasis prevalence and intensity of infection was conducted by searching at PubMed, LILACS and EMBASE. Experts on the topic were informally consulted and institutional web pages were reviewed (PAHO/WHO, Ministries of Health). Only SCH infection among children was registered because it can be a 'proxi-indicator' of recent transmission by the time the study is conducted. PRINCIPAL FINDINGS: One hundred thirty two full-text articles met the inclusion criteria and provided 1,242 prevalence and 199 intensity of infection data points. Most of them were from Brazil (69.7%). Only Brazil published studies after 2001, showing several 'hot spots' with high prevalence. Brazil, Venezuela, Suriname and Saint Lucia need to update the epidemiological status of schistosomiasis to re-design their national programs and target the elimination of Schistosoma mansoni transmission by 2020. In Antigua and Barbuda, Dominican Republic, Guadeloupe, Martinique, Montserrat and Puerto Rico schistosomiasis transmission may be interrupted. However the compilation of an elimination dossier and follow-up surveys, per WHO recommendations, are needed to verify that status. Hence, the burden of subtle SCH chronic infection may be still present and even high in countries that may have eliminated transmission. Heterogeneity in the methodologies used for monitoring and evaluating the progress of the schistosomiasis programs was found, making cross-national and chronological comparisons difficult. CONCLUSIONS: There is a need for updating the schistosomiasis status in the historically endemic countries and territories in LAC to address the required public health interventions for control and elimination programs or to verify the elimination of transmission of Schistosoma mansoni. Improved reporting and standardization of the monitoring and evaluation methodologies used are recommended, while using available WHO guidelines. Meeting a regional elimination goal will require additional and improved epidemiological data by age group and sex.

High prevalence of soil-transmitted helminths in Southern Belize-highlighting opportunity for control interventions.

OBJECTIVE: To assess prevalence and intensity of soil-transmitted helminths (STH) in school age children of two southern districts as baseline information prior to implement a deworming program against intestinal parasites as part of an integrated country development plan. METHODS: Children randomly selected from urban and rural schools in Southern Belize provided one stool sample each, analysed by the Kato-Katz method to assess prevalence and intensity of STH infections. Epi Info software was used for data analysis; Chi-square test and Fischer exact test were applied to compare group proportions; P<0.05 was considered of statistical significance; descriptive statistics were expressed as percentages. RESULTS: A total of 500 children from 10 schools participated in the study from May to December 2005. Prevalence of STH ranged between 40% and 82% among schools, with a median of 59.2%; the majority of light intensity, and with 2.2% high intensity infection. Trichuris and Ascaris infections presented similar frequency in children aged from 6 to 9 years old; hookworm infections tended to be more frequent in the older group 10 to 12 years old. Statistical significances (P≤0.01) were found in children in rural schools infected with any species of STH, in moderate Trichuris infections, in hookworm infections in rural areas with strong Mayan presence and in Ascaris infections in children of Mayan origin. CONCLUSIONS: High prevalence of STH in Southern Belize provided sound ground for implementing an integrated deworming control program.

[The road to elimination: an overview of neglected infectious diseases in Latin America and the Caribbean]. / El camino a la eliminación: un panorama de las enfermedades infecciosas desatendidas en América Latina y el Caribe.

Neglected infectious diseases (NID) affect mainly isolated populations living in isolation and in poor socioeconomic conditions. These diseases, by their chronic and silent nature, often affect communities with a weak political voice. This translates into very little attention or political priority; which is reflected in minimal and insufficient preventive measures, monitoring and control. However, there is evidence this situation is changing favorably in some countries of the Americas. In recent years, several resolutions (official agreement of the member countries of the Pan American Health Organization / World Health Organization-PAHO / WHO), regional and global agreements on public health; with a greater commitment from the pharmaceutical industry, and other donors and international partners in combination with the development and use of integrated action plans have allowed countries to intensify public interventions to control these diseases and thus achieve target elimination of NID. Onchocerciasis, lymphatic filariasis, Chagas disease, leprosy and trachoma blindness, among others, have been eliminated in several countries and endemic areas, regardless of the level of development of the country or geographical area where they are located. The political decision reflected in adequate financial resources in the next decade will be crucial to achieving the goals of elimination of NID (regional and national).

El camino a la eliminación: un panorama de las enfermedades infecciosas desatendidas en América Latina y el Caribe / The road to elimination: an overview of neglected infectious diseases in Latin America and the Caribbean

Las enfermedades infecciosas desatendidas (EID) afectan, principalmente, a las poblaciones que viven en condiciones aisladas y socioeconómicas de pobreza. Estas enfermedades, por su naturaleza crónica y silenciosa, aquejan con frecuencia a comunidades con voz política débil. Lo anterior se traduce en muy poca atención o prioridad política; lo que se refleja en mínimas e insuficientes acciones de prevención, vigilancia y control. Sin embargo, hay evidencia de que la situación está cambiando favorablemente en algunos países de las Américas. En los últimos años, varias resoluciones (acuerdos oficiales de los países miembros de la Organización Panamericana de la Salud/Organización Mundial de la Salud- OPS/OMS), convenios regionales y mundiales en materia de salud pública, junto a un mayor compromiso por parte de la industria farmacéutica, y otros donantes y socios internacionales, en combinación con el desarrollo y uso de los planes de acción integrados, han permitido que los países intensifiquen las intervenciones públicas hacia el control de estas enfermedades y así alcanzar los objetivos de eliminación de las EID. La oncocercosis, la filariasis linfática, la enfermedad de Chagas, la lepra y la ceguera por tracoma, entre otras, han sido eliminadas en varios países o zonas endémicas, sin importar el nivel de desarrollo del país o área geográfica donde se localizan. La voluntad política reflejada en los recursos financieros suficientes en la próxima década, serán determinantes para lograr los objetivos regionales y nacionales de eliminación de las EID...

Neglected infectious diseases (NID) affect mainly isolated populations living in isolation and in poor socioeconomic conditions. These diseases, by their chronic and silent nature, often affect communities with a weak political voice. This translates into very little attention or political priority; which is reflected in minimal and insufficient preventive measures, monitoring and control. However, there is evidence this situation is changing favorably in some countries of the Americas. In recent years, several resolutions (official agreement of the member countries of the Pan American Health Organization / World Health Organization-PAHO / WHO), regional and global agreements on public health; with a greater commitment from the pharmaceutical industry, and other donors and international partners in combination with the development and use of integrated action plans have allowed countries to intensify public interventions to control these diseases and thus achieve target elimination of NID. Onchocerciasis, lymphatic filariasis, Chagas disease, leprosy and trachoma blindness, among others, have been eliminated in several countries and endemic areas, regardless of the level of development of the country or geographical area where they are located. The political decision reflected in adequate financial resources in the next decade will be crucial to achieving the goals of elimination of NID (regional and national)...

Update on the mapping of prevalence and intensity of infection for soil-transmitted helminth infections in Latin America and the Caribbean: a call for action.

It is estimated that in Latin America and the Caribbean (LAC) at least 13.9 million preschool age and 35.4 million school age children are at risk of infections by soil-transmitted helminths (STH): Ascaris lumbricoides, Trichuris trichiura and hookworms (Necator americanus and Ancylostoma duodenale). Although infections caused by this group of parasites are associated with chronic deleterious effects on nutrition and growth, iron and vitamin A status and cognitive development in children, few countries in the LAC Region have implemented nationwide surveys on prevalence and intensity of infection. The aim of this study was to identify gaps on the mapping of prevalence and intensity of STH infections based on data published between 2000 and 2010 in LAC, and to call for including mapping as part of action plans against these infections. A total of 335 published data points for STH prevalence were found for 18 countries (11.9% data points for preschool age children, 56.7% for school age children and 31.3% for children from 1 to 14 years of age). We found that 62.7% of data points showed prevalence levels above 20%. Data on the intensity of infection were found for seven countries. The analysis also highlights that there is still an important lack of data on prevalence and intensity of infection to determine the burden of disease based on epidemiological surveys, particularly among preschool age children. This situation is a challenge for LAC given that adequate planning of interventions such as deworming requires information on prevalence to determine the frequency of needed anthelmintic drug administration and to conduct monitoring and evaluation of progress in drug coverage.

The Pan American Health Organization's role and perspectives on the mapping and modeling of the neglected tropical diseases in Latin America and the Caribbean: an overview.

The Pan American Health Organization (PAHO), which functions as the regional office for the Americas of the World Health Organization, is committed to provide technical cooperation to countries to update the epidemiological information available for mapping and modelling of the neglected tropical diseases (NTDs), a set of diseases mainly caused by parasites affecting people living in low socioeconomic and favourable environmental conditions. This communication discusses PAHO's role and perspectives in the use of mapping and modelling of these diseases with a view to promote its use in the development and implementation of integrated, inter-programmatic and inter-sectoral plans for the prevention, control or elimination of the NTDs and other infectious diseases related to poverty.

Administration of triclabendazole is safe and effective in controlling fascioliasis in an endemic community of the Bolivian Altiplano.

BACKGROUND: The Bolivian northern Altiplano is characterized by a high prevalence of Fasciola hepatica infection. In order to assess the feasibility, safety and efficacy of large-scale administration of triclabendazole as an appropriate public health measure to control morbidity associated with fascioliasis, a pilot intervention was implemented in 2008. MATERIALS AND METHODS: Schoolchildren from an endemic community were screened for fascioliasis and treated with a single administration of triclabendazole (10 mg/kg). Interviews to assess the occurrence of adverse events were conducted on treatment day, one week later, and one month after treatment. Further parasitological screenings were performed three months after treatment and again two months later (following a further treatment) in order to evaluate the efficacy of the intervention. RESULTS: Ninety infected children were administered triclabendazole. Adverse events were infrequent and mild. No serious adverse events were reported. Observed cure rates were 77.8% after one treatment and 97.8% after two treatments, while egg reduction rates ranged between 74% and 90.3% after one treatment, and between 84.2% and 99.9% after two treatments. The proportion of high-intensity infections (≥ 400 epg) decreased from 7.8% to 1.1% after one treatment and to 0% after two treatments. CONCLUSION: Administration of triclabendazole is a feasible, safe and efficacious public health intervention in an endemic community in the Bolivian Altiplano, suggesting that preventive chemotherapy can be applied to control of fascioliasis. Further investigations are needed to define the most appropriate frequency of treatment.

Elimination of neglected diseases in latin america and the Caribbean: a mapping of selected diseases.

In Latin America and the Caribbean, around 195 million people live in poverty, a situation that increases the burden of some infectious diseases. Neglected diseases, in particular, are often restricted to poor, marginalized sections of the population. Tools exist to combat these diseases, making it imperative to work towards their elimination. In 2009, the Pan American Health Organization (PAHO) received a mandate to support the countries in the Region in eliminating neglected diseases and other poverty-related infections. The objective of this study is to analyze the presence of selected diseases using geo-processing techniques. Five diseases with information available at the first sub-national level (states) were mapped, showing the presence of the disease ("hotspots") and overlap of diseases ("major hotspots"). In the 45 countries/territories (approximately 570 states) of the Region, there is: lymphatic filariasis in four countries (29 states), onchocerciasis in six countries (25 states), schistosomiasis in four countries (39 states), trachoma in three countries (29 states), and human rabies transmitted by dogs in ten countries (20 states). Of the 108 states with one or more of the selected diseases, 36 states present the diseases in overlapping areas ("major hotspots"). Additional information about soil-transmitted helminths was included. The analysis suggests a majority of the selected diseases are not widespread and can be considered part of an unfinished agenda with elimination as a goal. Integrated plans and a comprehensive approach, ensuring access to existing diagnostic and treatment methods, and establishing a multi-sectoral agenda that addresses social determinants, including access to adequate water and sanitation, are required. Future studies can include additional diseases, socio-economic and environmental variables.

The neglected tropical diseases of Latin America and the Caribbean: a review of disease burden and distribution and a roadmap for control and elimination.

The neglected tropical diseases (NTDs) represent some of the most common infections of the poorest people living in the Latin American and Caribbean region (LAC). Because they primarily afflict the disenfranchised poor as well as selected indigenous populations and people of African descent, the NTDs in LAC are largely forgotten diseases even though their collective disease burden may exceed better known conditions such as of HIV/AIDS, tuberculosis, or malaria. Based on their prevalence and healthy life years lost from disability, hookworm infection, other soil-transmitted helminth infections, and Chagas disease are the most important NTDs in LAC, followed by dengue, schistosomiasis, leishmaniasis, trachoma, leprosy, and lymphatic filariasis. On the other hand, for some important NTDs, such as leptospirosis and cysticercosis, complete disease burden estimates are not available. The NTDs in LAC geographically concentrate in 11 different sub-regions, each with a distinctive human and environmental ecology. In the coming years, schistosomiasis could be eliminated in the Caribbean and transmission of lymphatic filariasis and onchocerciasis could be eliminated in Latin America. However, the highest disease burden NTDs, such as Chagas disease, soil-transmitted helminth infections, and hookworm and schistosomiasis co-infections, may first require scale-up of existing resources or the development of new control tools in order to achieve control or elimination. Ultimately, the roadmap for the control and elimination of the more widespread NTDs will require an inter-sectoral approach that bridges public health, social services, and environmental interventions.

Intersectoral approaches to neglected diseases.

The neglected diseases are a diverse group of communicable diseases that affect principally the world's poorest people. They are linked to poverty, as both a cause and a consequence of same, and affect community security and family productivity. The neglected diseases cause acute and chronic illness, disability, and sometimes death, and they may carry stigma for those infected. Current interventions for neglected diseases emphasize the health sector, but to achieve sustainability and simultaneously combat poverty, an intersectoral approach to their prevention and control is needed. This chapter outlines some concepts for an intersectoral approach, including interventions from the nutrition and food security, education, and environmental sectors.