BackgroundDengue is an emerging health problem in several coastlines along the Red Sea. The objective of the present work is to elucidate spatial and temporal patterns of dengue transmission in Port Sudan.Methods/FindingsA longitudinal study with three cross-sectional surveys was carried out in upper, middle and lower class neighborhoods, from November 2008 to October 2009. Monthly, entomological surveys were followed by serological surveys in dengue vector-positive houses. Meteorological records were obtained from two weather stations in the city during the same time. Overall, 2825 houses were inspected. Aedes aegypti represented 65% (35,714/54,944) and 68% (2526/3715) of the collected larvae and pupae, respectively. Out of 4640 drinking water containers, 2297 were positive for Ae. aegypti. Clay-pots “Zeirr” followed by plastic barrels were key productive containers for pupae of dengue vector, 63% (n = 3959) and 26% (n = 1651), respectively. A total of 791 blood samples were tested using PanBio Capture/Indirect IgM ELISA. Overall, the sero-prevalence rate of dengue ranged between 3%–8% (41/791), compared to an incidence of 29–40 new cases per 10,000 (193/54886) in the same examined population. Lower and middle class neighborhoods had higher entomological indices compared with upper class ones (p<0.001). Although, dengue incidence rate was significantly lower in the middle and lower class neighborhoods (F = 73.97, d.f. = 2, p<0.001), no difference in IgM prevalence was shown. The city is subject to two transmission peaks in the winter (i.e. November–January), and summer (i.e. June–August). The serological peaks of dengue are preceded by entomological peaks that occur before the onset of winter (November) and summer (March) respectively.ConclusionDengue incidence is heterogeneously distributed across the neighborhoods of Port Sudan and exhibits a bi-cyclic intra-annual pattern. Hence, it should be feasible to carry out timely vector control measures to prevent or reduce dengue transmission.

An unprecedented dengue outbreak occurred in 2010 in Port Sudan city, Sudan. Dengue incidence was 94 cases per 10 000 observed over 17 epidemiological weeks (total cases = 3 765). We report here the impact of the vector control response plan to the outbreak, which mainly entailed house inspection and insecticide space spraying. In total 3 048 houses were inspected during vector surveillance and 19 794 larvae and 3 240 pupae of Aedes aegypti were collected. Entomological indices decreased during the period: house index declined from 100% to 16% (F = 57.8, P < 0.001) and pupal/person (P/P) index from 0.77 to 0.10 (F = 3.06, P < 0.01) in weeks 9 and 21 respectively. This decline was accompanied by a decrease in cases from a peak of 341 cases in week 13 to zero in week 29 and the end of the outbreak. There was a significant correlation between the entomological parameters and dengue incidence (R 2 = 0.83, F= 23.9, P < 0.001). Integrated epidemiological and vector surveillance is essential to an effective dengue control programme Surveillance du vecteur de la dengue et actions de lutte pendant une importante flambée dans une zone côtière de la Mer rouge au Soudan RÉSUMÉ Une flambée de dengue sans précédent s'est produite en 2010 dans la ville de Port Soudan (Soudan). L'incidence de la dengue était de 94 cas pour 10 000 observés pendant 17 semaines épidémiologiques (nombre total de cas = 3 765). Nous présentons ici l'impact du plan de riposte visant à lutter contre le vecteur de la flambée. Ce plan consistait principalement en l'inspection des logements et la pulvérisation d'insecticides. Au total, 3 048 logements ont été inspectés pendant la surveillance du vecteur et 19 794 larves et 3 240 nymphes d'Aedes aegypti ont été recueillies. Les indices entomologiques ont diminué pendant la période : l'indice « habitations » est passé de 100 % à 16 % (F = 57,8 ; P < 0,001) et l'indice nymphe/personne est passé de 0,77 à 0,10 (F = 3,06 ; P < 0,01) au cours des semaines 9 et 21 respectivement. Cette diminution a été accompagnée par une diminution du nombre de cas, passant d'un pic de 341 cas en semaine 13 à zéro en semaine 29 et à la fin de la flambée. Une corrélation significative a été retrouvée entre les paramètres entomologiques et l'incidence de la dengue (R 2 = 0,83 ; F= 23,9 ; P < 0,001). Une surveillance vectorielle et épidémiologique intégrée est essentielle pour garantir l'efficacité d'un programme de lutte contre la dengue.