In the early summer of 1993, an outbreak of Rift Valley fever (RVF) was reported among both humans and animals in Aswan Governorate, Upper Egypt. To determine whether RVF infection had spread to the Nile delta region of the country, we carried out a cross-sectional survey of 1181 occupationally exposed abattoir workers (97% male; age 10-72 years) in 15 governorates of Egypt in November 1993. Th...