In vivo and in vitro translation studies have shown that genomic RNA of simian hemorrhagic fever (SHF) virus codes for both structural and nonstructural polypeptides. Virions were shown to contain 3 structural polypeptides of approximately 50K, 18K and 12K, the largest of which is a glycoprotein. SHF virus RNA also was found to have a type 1 cap structure. In these characteristics, SHF virus has the replication strategy, number of type of polypeptides and cap structure of Flaviviridae, a recently formed virus family.