Dengue in Southeast Asia: epidemiological characteristics and strategic challenges in disease prevention / Dengue no Sudeste Asiático: características epidemiológicas e desafios estratégicos na prevenção da doença

Dengue emerged as a public health burden in Southeast Asia during and following the Second World War and has become increasingly important, with progressively longer and more frequent cyclical epidemics of dengue fever/dengue hemorrhagic fever. Despite this trend, surveillance for this vector-borne viral disease remains largely passive in most Southeast Asian countries, without adequate laboratory support. We review here the factors that may have contributed to the changing epidemiology of dengue in Southeast Asia as well as challenges of disease prevention. We also discuss a regional approach to active dengue virus surveillance, focusing on urban areas where the viruses are maintained, which may be a solution to limited financial resources since most of the countries in the region have developing economies. A regional approach would also result in a greater likelihood of success in disease prevention since the large volume of human travel is a major factor contributing to the geographical spread of dengue viruses.

A dengue emergiu como problema de saúde pública no Sudeste Asiático durante e após a Segunda Guerra Mundial, e vem se agravando cada vez mais, com epidemias cíclicas progressivamente mais longas e freqüentes de dengue e de febre hemorrágica da dengue. Apesar dessa tendência, a vigilância dessa virose transmitida por vetores permanece basicamente passiva na maioria dos países do Sudeste Asiático, sem apoio laboratorial adequado. O artigo apresenta uma revisão dos fatores que podem ter contribuído para a mudança no perfil epidemiológico da dengue na região, além de discutir os desafios para a prevenção da doença. Analisa-se também uma abordagem regional para a vigilância ativa dos vírus da dengue, focando as áreas urbanas onde eles se mantêm, o que pode representar uma solução à limitação de recursos financeiros, uma vez que a maioria dos países da região tem economias em desenvolvimento. Uma abordagem regional também resultaria em maior probabilidade de sucesso na prevenção da doença, já que a grande circulação de viajantes na região é um fator importante na disseminação dos vírus da dengue.

Dengue in Grenada / El dengue en el país de Granada

Objetivos. La fiebre del dengue es endémica en el país caribeño de Granada y es grande su subnotificación como fuente de morbilidad. El objetivo del presente estudio fue evaluar la situación del dengue en una comunidad representativa de ese país. Métodos. Se llevaron a cabo encuestas en la zona del valle de Mont Tout y de Grand Anse, en la parroquia de St. George's, de marzo a junio de 1996. Los objetivos de las encuestas fueron: 1) explorar los conocimientos, actitudes y prácticas (CAP) de los habitantes; 2) determinar la presencia de formas larvarias y adultas de Aedes aegypti en posibles criaderos, y 3) identificar la seroprevalencia de inmunoglobulina G (IgG) con actividad específica contra el virus del dengue en la población local. Resultados. De las 102 personas que respondieron la encuesta de CAP, 100 (98%) indicaron que nunca habían padecido de fiebre del dengue. De las 75 personas que consintieron que se les sacaran muestras de sangre, 70 (93%) (intervalo de confianza de 95% = 85,1%­97,8%) tuvieron resultados positivos en la prueba de inmunoadsorción enzimática para la detección de IgG, señal de que habían tenido una exposición anterior. En lo que respecta al almacenamiento del agua, 98 de las 102 personas (96%) encuestadas almacenaban agua fresca en recipientes. La encuesta de vectores reveló que en 57 de las 102 viviendas (56%) había larvas de Ae. Aegypti en recipientes de agua en la propiedad, y en 94 de las 102 viviendas (92%) se encontraron mosquitos Ae. aegypti adultos en el interior. Conclusiones. A pesar de que muchas personas estaban familiarizadas con la fiebre del dengue y el mosquito vector, la encuesta de 1996 reveló en ellas conocimientos incompletos acerca de las relaciones importantes entre los mosquitos, los hábitos del ser humano y la transmisión de la enfermedad. Desde 1996 se han puesto en marcha de continuo iniciativas educativas en las escuelas públicas y mediante campañas sanitarias a escala nacional, pero pocas han estado dirigidas específicamente a la comunidad aquí estudiada. Estos datos indican que el país de Granada necesita un sistema de educación comunitaria continua que se oriente a reducir la transmisión de la fiebre del dengue y la población de Ae. aegypti

Objectives. Dengue fever is endemic in the country of Grenada and is grossly underreported as a source of morbidity. The goal of this study was to assess the status of dengue fever in a representative community in Grenada. Methods. Surveys were conducted in the Mont Tout/Grand Anse Valley area in the parish of St. George's from March to June 1996. The objectives of the survey were to: (1) to assess the knowledge, attitudes, and practices (KAP) of residents; (2) to determine the presence of larval and adult Aedes aegypti and their potential breeding sites; and (3) to identify the seroprevalence of specific immunoglobulin G (IgG) dengue antibodies in the local population. Results. Out of the 102 respondents to the KAP survey, 100 of them (98%) reported never having had dengue fever. Of the 75 persons who agreed to have blood samples taken, 70 of them (93%) (95% confidence interval = 85.1%­97.8%) tested positive with the IgG enzyme-linked immunosorbent assay, indicating past exposure. In terms of water storage, 98 of 102 respondents (96%) stored fresh water in containers. The vector survey found 57 of the 102 households (56%) had Ae. aegypti larvae in water containers on their property, and 94 of 102 dwellings (92%) had adult Ae. aegypti mosquitoes indoors. Conclusions. Although many people were familiar with dengue fever and mosquitoes, the 1996 survey found that their knowledge of the important relationships among mosquitoes, human behavior, and disease transmission was incomplete. Since 1996, continued education efforts have been made in the public school system and with national public health campaigns, yet little effort has been specifically targeted towards our study community. These data suggest Grenada has a need for continued community education that addresses dengue fever transmission and Ae. aegypti reduction

Guidelines on the cost-effectiveness of larval control programs to reduce dengue transmission in Puerto Rico / Guía de rentabilidad de los programas de control de larvas para reducir la transmisión del dengue en Puerto Rico

OBJECTIVE: In the past 20 years, the emphasis for avoiding dengue epidemics has focused on larval control of Aedes aegypti, the principal mosquito vector of dengue viruses. A general consensus is that mosquito larval control holds the best promise for reducing dengue epidemics, although its actual effectiveness is still unknown and subject to a great deal of uncertainty. The objective of this research was to assess the cost-effectiveness of emergency larval control programs for reducing dengue transmission in the Caribbean island of Puerto Rico and to develop guidelines to help choose between carrying out a rapid-response, emergency larval control intervention and not conducting such an intervention. DESIGN AND METHODS: Data on dengue transmission and its likely impacts in Puerto Rico were used as a case study to develop intervention guidelines. A distribution of economic impacts was simulated using available data on disease rates and economic variables, including the costs of treating patients and the opportunity costs represented by lost wages. Successful larval control interventions were assessed by determining two parameters: (1) the costs of an intervention and (2) the expected reduction in the reported case rate of dengue. In addition, we examined how these guidelines would change with an early warning system that provides information on a possible outbreak of dengue. RESULTS: In Puerto Rico, larval control programs that are expected to reduce dengue transmission by 50 percent and cost less than US$ 2.50 per person will be cost-effective. Programs that cost more per person but that further reduce transmission are still likely to be cost-effective. Having an early warning system, even one that provides a low level of accuracy, can extend the range of larval control programs that are cost-effective. For example, with an early warning system, a larval control program that reduces dengue transmission by 50 percent and that costs less than US$ 4.50 per person would be expected to be cost-effective. CONCLUSIONS: Guidelines such as the ones that we developed for Puerto Rico can be useful to public health authorities in helping to decide whether or not to spend resources for a larval control program to reduce dengue transmission. The range of larval control interventions that are cost-effective can be increased by having an early warning system that provides even a small amount of information regarding possible outbreaks

Objetivos. En los últimos 20 años, las medidas para evitar las epidemias de dengue se han centrado en el control de las larvas del mosquito Aedes aegypti, el principal vector de los virus del dengue. Existe consenso acerca de que el control de las larvas de mosquito es el método más prometedor para reducir las epidemias de dengue, a pesar de que su eficacia real aún se desconoce y constituye un elemento de gran incertidumbre. El objetivo de la presente investigación fue evaluar la rentabilidad de los programas de emergencia para el control de larvas, dirigidos a reducir la transmisión del dengue en la isla caribeña de Puerto Rico, y desarrollar una guía que permita decidir si se deben realizar o no intervenciones de emergencia para el control de larvas como respuesta rápida. Diseño y métodos. Los datos sobre la transmisión del dengue y su probable impacto en Puerto Rico fueron utilizados a manera de estudio de caso para desarrollar una guía de intervención. Se simuló una distribución de los valores de impacto económico utilizando para ello los datos disponibles de morbilidad y variables económicas, entre ellas el costo del tratamiento de los pacientes y los costos de oportunidad que representan los salarios perdidos. El éxito de las intervenciones de control de larvas fue evaluado mediante dos parámetros: (1) el costo de una intervención y (2) la reducción esperada de casos reportados de dengue. Adicionalmente, se examinó cómo esta guía podría variar con un sistema de alerta rápida que avise de posibles brotes de dengue. Resultados. En Puerto Rico, los programas de control de larvas que prevean reducir la transmisión en 50% y que cuesten menos de US$ 2,50 por persona serán rentables. Los programas que cuesten más por persona pero que logren mayores reducciones de la transmisión de la enfermedad pueden aun ser rentables. Los sistemas de alerta rápida, incluso si su nivel de exactitud es bajo, pueden hacer que más programas para el control de larvas sean rentables. Por ejemplo, podría esperarse que con un sistema de alerta rápida, un programa que reduzca la transmisión del dengue en menos de 50% y cuyo costo sea menor de US$ 4,50 por persona, sea rentable. Conclusiones. Guías como esta, desarrollada para Puerto Rico, pueden ayudar a las autoridades sanitarias a decidir si deben dedicar o no recursos a un programa de control de larvas para reducir la transmisión del dengue. El número de intervenciones rentables para el control de larvas puede aumentar mediante la implementación de un sistema de alerta rápida que facilite información acerca de posibles brotes, aun cuando esta sea escasa

Emergence and Global Spread of a Dengue Serotype 3; Subtype III Virus

Over the past two decades; dengue virus serotype 3 (DENV-3) has caused unexpected epidemics of Dengue hemorrhagic fever (DHF) in Sri Lanka; East Africa; and Latin America. We used a phylogenetic approach to evaluate the roles of virus evolution and transport in the emergence of these outbreaks. Isolates from these geographically distant epidemics are closely related and belong to DENV-3; subtype III; which originated in the Indian subcontinent. The emergence of DHF in Sri Lanka in 1989 correlated with the appearance there of a new DENV-3; subtype III variant. This variant likely spread from the Indian subcontinent into Africa in the 1980s and from Africa into Latin America in the mid-1990s. DENV-3; subtype III isolates from mild and severe disease outbreaks formed genetically distinct groups; which suggests a role for viral genetics in DHF

Epidemic dengue 4 in the Yucatán, México, 1984

An outbreak of dengue 4 occurred in the Yucatán, México in 1984. During the course of the outbreak, 538 of 5486 reported cases of dengue-like illness were studied; 200 were confirmed as dengue serologically and/or virologically. Dengue 4 virus was isolated from 34 patients and dengue 1 from one. Severe haemorrhagic symptoms were observed in 9 laboratory confirmed patients, including four deaths. Thus, the outbreak in Yucatán is the second dengue epidemic in the Americas after the Cuban epidemic in 1981 in which a number of patients suffered from haemorrhagic complications. It was notable that 5 of 9 hospitalized, severe cases were young adults and that only one met the WHO criteria of DHF, in contrast to primary pediatric nature of DHF in Southeast Asia. In this paper we describe clinical, serologic, and virologic studies conducted during the outbreak.

Dengue and dengue hemorrhagic fever in the Americas

Durante los pasados 15 años ha habido un aumento constante en la incidencia de dengue en las Américas. Esto ha sido causado por un aumento en la mayoría de los países de la frecuencia de epidemias de dengue resultado del aumento en el número de serotipos de los virus que circulan en la región. El cambio en la ecología de la enfermedad ha resultado en la aparición del dengue hemorrágico/síndrome de "shock" de dengue (DH/DSS) en la región, primero con una gan epidemia en Cuba, seguido por el aumento en la ocurrencia de casos esporádicos de DH/DSS en muchos países. La secuela de eventos en las Américas en la década de los 80 ha sido casi idéntica al patrón observalo en la década de los 50 en el Sureste de Asia. Por lo tanto, el panorama sobre la prevención de epidemias de DH/DSS en la región Americana no es bueno. En la ausencia de erradiación del mosquito Aedes aegypti, la única esperanza para una prevención y control efectivos es desarrollar más sistemas efectivos de vigilancia para DH/DSS y combinar estos con programas de emergencia de control de vectores basados en la comunidad