The sequence of the S (small) RNA segment of the ArD 44313 isolate of Dugbe nairovirus (DUG) has been redetermined, and a number of apparent errors in the previously reported sequence (V K Ward, A. C. Marriott, A. A, El-Ghorr, and R A. Nuttall, 1990, Virology 175, 518-524) were revealed. Our results indicate that the S RNA is 1716 nucleotides (nt) in length and contains one large open reading frame spanning 1449 nt. This can encode a 483 amino acid polypeptide, M, 53.9 kDa, corresponding to the viral nucleocapsid protein N. The DUG N protein is thus similar in length to the N proteins of Hazara (HAZ) and Crimean-Congo haemorrhagic fever (CCHF) nairoviruses, which are 485 and 482 amino acids in length, respectively, S segment RNA sequences were also determined for DUG isolates IbAr 1792, IbH 11480, ArD 16095, and KT 281/75; only the KT 281/76 sequence differed markedly from that of ArD 44313. Phylogenetic trees were constructed for these nairovirus S segment sequences. (C) 2002 Elsevier Science (USA).