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.

Guidelines on the cost-effectiveness of larval control programs to reduce dengue transmission in 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

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