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.

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)...

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.

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.