Virus isolations and high population density implicate Culex antennatus (Becker) (Diptera: Culicidae) as a vector of Rift Valley Fever virus during an outbreak in the Nile Delta of Egypt

► We report for the first time multiple isolations of Rift Valley fever (RVF) virus from naturally infected Culex antennatus mosquitoes collected in Egypt during the 2003 RVF outbreak. ► RVF virus was detected in human clinical samples over the period of June-October, 2003 in the Nile Delta Governorates of Kafr el Sheikh and Behira. ► The World Health Organization reported 45 cases of RVF including 17 deaths in the Sidi Salim District of Kafr el Sheikh. ► Entomologic investigations collected, identified, and tested host-seeking female mosquitoes for the presence of pathogenic viruses.