[Sero-epidemiological study of West Nile virus circulation in human in Tunisia].

West Nile virus (WNV) is an arbovirus classified into the family of Flaviviridae, genus Flavivirus. It is responsible for neurological diseases that occurred frequently as outbreaks and considered as an emerging infection in different regions of the world. In Tunisia, two outbreaks of meningoencephalitis due to this virus occurred, in 1997 and 2003. The virus circulation is studied only in Sahel, region affected by the two epidemics. The aim of this study is to determine if WNV is present in other regions of the country where, up to now, no data are available. A total of 1,854 sera collected from healthy patients were investigated by ELISA to detect specific IgG, during January to December 2007. Patients included are from three governorates: Kairouan, Bizerte, and Sfax. The governorate of Sfax (center of Tunisia) was affected by the two outbreaks, whereas only two cases were observed previously at Kairouan and no cases at Bizerte. Specific IgG were detected in 12.5% of studied population. This seroprevalence varied largely between the three governorates studied. Globally, three regions with different endemicity were described: high endemicity at Kairouan (27.7%), moderate at Sfax (7.5%), and low at Bizerte (0.7%). At Kairouan, the seroprevalence is significantly higher in individuals aged over 40. Our results suggest that WNV circulates in Tunisia; it has a high risk not only in regions affected by previous outbreaks but throughout the country. An active surveillance should be instituted in the country. It must target individuals, and animals, which can be vectors or reservoirs for the virus.