Rift Valley fever virus: some ultrastructural observations on material from the outbreak in Egypt 1977

London School of Hygiene and Tropical Medicine, Keppel Street, London WC1 Kouka S. E. Abdel Wahab Girls' College, Al Azhar University, Cairo, Egypt Rift Valley fever virus isolates from the 1977 outbreak in Egypt were studied at an ultrastructural level. The particles measured 90 to 110 nm in diam. using negative staining and sectioning techniques, with a core component of 80 to 85 nm. The surface of the virions was calculated to be covered by approx. 160 sub-units. The particles were found in smooth endoplasmic reticular systems, which were made up of either multi-tubular complexes, or of a single large vacuole. The majority of these membrane systems were found to be unassociated with Golgi apparatus. Inclusion bodies were found within the host cell nuclei (made up of rods and fine granules) and in the cytoplasm (aggregates of fine or coarse granules). The possible relationship of these structures to virus replication is discussed. Received 24 July 1978; accepted 23 August 1978.