Exploratory space-time analysis of dengue incidence in Trinidad: a retrospective study, 1998-2004

OBJECTIVE: To obtain an understanding of the space and time dynamics of dengue and provide health agencies with important clues for reducing its impact. DESIGN AND METHODS: Dengue Haemorrhagic Fever (DHF) cases observed for the period 1998-2004 were georeferenced using Geographic Information System software. Spatial clustering was calculated for individual years and for the entire study period using the Nearest Neighbor Index. Space and time interaction between DHF cases was determined using the Knox Test while the Nearest Neighbor Hierarchical method was used to extract DHF hot spots. All space and time distances calculated were validated using the Pearson r significance test. RESULTS: Results shows that (1) a decrease in mean distance between DHF cases correlates with activity leading up to an outbreak, (2) a decrease in temporal distance between DHF cases leads to increased geographic spread of the disease, with an outbreak occurrence about every 2 years, and (3) a general pattern in the movement of dengue incidents from more rural to urban settings leading up to an outbreak with hotspot areas associated with transportation hubs. CONCLUSION: The results of this study can be used by public health officers to help visualize and understand the spatial and temporal patterns of dengue, and to prepare warnings for the public. Dengue space-time patterns and hotspot detection will provide useful information to support public health officers in their efforts to control and predict dengue spread over critical hotspots allowing better allocation of resources.

Impact of pre-seasonal focal treatment on population densities of the mosquito Aedes aegypti in Trinidad, West Indies: a preliminary study.

A new pre-seasonal focal treatment strategy against Aedes aegypti L. (Diptera: Culicidae) mosquitoes is described for the first time. It was evaluated for 25 weeks using ovitraps, and larval and pupal surveys in the townships of Curepe (treated) and St. Joseph (untreated), Trinidad, West Indies. Both townships were similar with respect to number of houses, size of human populations, the number of Ae. aegypti infested houses and containers. In March 2003, a total of 9403 containers were inspected, of which 1.4 per cent in Curepe (63/4499) and 1.3 per cent in St. Joseph (64/4904) were positive for Ae. aegypti immature stages. Curepe had a lower percentage (12.7 per cent) of the main type of breeding container present (small miscellaneous containers) than St. Joseph (28.1 per cent). Following focal treatment during the month of April (2-3 weeks before the onset of the rainy season), the Ae. aegypti population declined significantly (P>0.01) from a Breteau index (BI; proportion of containers positive for larvae and pupae) of 19.0 to a minimum of 6.0 and a pupae/person index (PI) of 1.23 to a minimum of 0.35 in May, while in the untreated town of St. Joseph, the BI steadily increased from 23 to 38 and the PI rose from 0.96 to 2.00 in August. Similar declines in other measures of population density (the number of positive houses and number of eggs collected in ovitraps) were observed in Curepe, while St. Joseph maintained PI of >1.50 and BI of >28. Furthermore, the Curepe Ae. aegypti population did not return to pre-treatment levels until 9-11 weeks after treatment, far beyond the 6 weeks normally expected during vector suppression campaigns.

The elderly in Trinidad: health, social and economic status and issues of loneliness / Personas de la tercera edad en Trinidad: salud, problemas y estatus social y económico, así como problemas de la soledad

OBJECTIVES: To determine the general health and social status of elderly persons surveyed in Trinidad and to explore issues of loneliness. METHOD: An island-wide survey of persons aged 65 years and older was conducted in early 2002 in Trinidad. Eight hundred and forty-five (845) elderly persons were chosen using systematic random sampling. The main survey instrument for data collection was a questionnaire that included structured as well as open-ended questions. The subjects were chosen in a house-to-house survey conducted in all eight counties in Trinidad. Elderly people who were unable to comprehend the questions were excluded from the survey. RESULTS: Those selected ranged in age from 65-102 years and represented all the ethnic groups in Trinidad. These elderly persons lived in a wide range of housing situations. The majority lived in the homes of family members (57%) and 16% lived on their own. A large proportion (80%) had at least one chronic medical problem, although 44% reported their health as "fairly good" or "good". More than a half of the males (53%) and 67% of the females were taking at least one prescribed medicine. The main sources of income were old age pension (85%) and National Insurance (15%). Thirty-three per cent reported feelings of loneliness. This figure includes 28% of those who did not live alone. CONCLUSION: The data revealed that across all ethnic groups more than one-third of the sample reported themselves to be in fair to good health. Many of these elders were lonely because their relatives were quite occupied with their own affairs.

OBJETIVOS: Determinar la salud general y el estatus social de personas de la tercera edad encuestadas en Trinidad, y explorar los problemas de la soledad. MÉTODO: Se llevó a cabo una encuesta en toda la isla de Trinidad a comienzos del 2002, con personas de 65 años de edad o más. Se escogieron ochocientos cuarenta y cinco (845) personas de la tercera edad mediante un muestreo aleatorio sistemático. El instrumento principal para la recolección de datos fue un cuestionario que incluía preguntas estructuradas así como preguntas abiertas. Los sujetos fueron escogidos en una encuesta conducida casa por casa en los ocho condados de Trinidad. Los ancianos y ancianas que no podían entender las preguntas, fueron excluidos de la encuesta. RESULTADOS: Los seleccionados tenían edades entre 65-102 años, y representaban todos los grupos étnicos de Trinidad. Estas personas mayores vivían en un amplio especto de situaciones de vivienda. La mayor parte de ellos vivía en hogares de miembros de su familia (57%) y el 16% vivían solos. Un gran número de ellos (80%) tenía por lo menos un problema médico crónico, aunque el 44% reportó que su salud era "bastante buena" o "buena." Más de la mitad de los hombres (53%) y el 67% de las mujeres se encontraban tomando al menos una medicina por prescripción médica. Las principales fuentes de ingreso fueron las pensiones por vejez (85%) y Seguro Nacional (15%). El treinta y tres por ciento reportó sentirse solo. Esta cifra incluye el 28% de los que no vivían solos. CCONCLUSIÓN: Los datos revelaron que en todos los grupos étnicos, más de un tercio de la muestra reportó su estado de salud entre bueno y satisfactorio. Muchas de estos ancianos y ancianas estaban solos porque sus familiares se hallaban muy ocupados con sus asuntos.