About twenty years ago, a dengue surveillance system was established in Guadeloupe and its outlying territories to detect the onset of epidemics, guide vector control efforts through the spatiotemporal monitoring of dengue cases, and identify circulating serotypes. This surveillance system consists of two main components: - the clinical component for monitoring suspected cases through a network of sentinel physicians - the serological component for monitoring confirmed cases through a network of laboratories In Saint Martin, the sentinel network consists of two general practitioners (out of 18 practicing physicians) and one hospital physician. Each week, the sentinel physicians are contacted by phone by the nurse from the Health Surveillance Unit (CVS) of the DSDS. The data collected include the number of suspected dengue cases who sought medical care during the previous week and the number of suspected cases hospitalized. Dengue serology tests are performed on-site by a private clinical laboratory (LABM-L) using a commercially available kit (Eurobio). The list of positive serology results is then faxed to the DSDS medical inspector in charge of health surveillance. The medical inspector then forwards to the Vector Control Unit (LAV) the addresses or residential neighborhoods of all confirmed and hospitalized cases, as well as grouped suspected cases. This information enables entomological investigations to be conducted and vector control measures to be implemented. Thus, the most recent dengue epidemic in the Caribbean was monitored using this system. It occurred from September 2001 to January 2002 and was caused by the DEN-3 serotype. It affected several Caribbean countries as well as Venezuela and Brazil. Since then, no major outbreak has occurred in Guadeloupe and its dependencies. It should be noted, however, that an outbreak occurred simultaneously on the islands of Saint Martin and Saint Barthélemy between December 2002 and January 2003; 31 suspected cases and 2 confirmed cases were then recorded in Saint Martin, and 30 suspected cases and 6 confirmed cases in Saint Barthélemy. It is commonly observed that dengue outbreaks generally begin in a very localized manner and that their spread is slow in the initial phase. As a result, a significant amount of time (several weeks) may elapse before the surveillance system detects an abnormal increase in cases and interventions can be organized, often too late to slow the transmission of the virus and prevent the spread of the disease. In fact, the network of sentinel physicians in Guadeloupe and its dependencies represents only one-fifth to one-tenth of all physicians, depending on the area, and the ordering of serological testing—far from being systematic—applies to only one in ten patients, even during the inter-epidemic period, despite recommendations issued since 1998. For this reason, it has been recommended that during inter-epidemic periods, an investigation be initiated for all confirmed outpatient cases, all suspected hospitalized cases, and all clusters¹ of suspected cases reported by sentinel physicians or spontaneously by physicians not belonging to the network. The objective of this investigation is to document and validate a potential outbreak in order to initiate vector control measures. It must include: - an entomological component (identification of the vector, types of breeding sites, assessment of entomological indices, etc.) - an epidemiological component (search for and identification of other suspected and/or confirmed cases among physicians and laboratories in the affected area, or directly at the visited clusters) To date, there is no investigation protocol or standard operating procedure in Guadeloupe. Such tools must therefore be developed based on experience gained during various interventions. These procedures may be modeled after those currently used by the mosquito control service in Martinique, established in 2000. (R.A.)