Division of Viral and Rickettsial Diseases, National Center for Infectious Diseases, Centers for Disease Control and Prevention, Atlanta, Georgia 30333.
Smallpox eradication culminated the most successful antimicrobial campaign in medical history. To characterize further the linear double-stranded DNA genome of the aetiological agent of smallpox, we have determined the entire nucleotide sequence of the highly virulent variola major virus, strain Bangladesh-1975 (VAR-BSH; 186,102 base pairs, 33.7% G + C; Genbank accession number, L22579). Here we highlight features of the molecule and focus on a few of the 187 putative proteins that probably contribute to pathogenicity and virus host-range properties. One hundred and fifty proteins were markedly similar to those of vaccinia virus (smallpox vaccine), for which a complete sequence has been reported for strain Copenhagen (VAC-CPN; 191,636 base pairs, 33.3% G + C). The remaining 37 proteins reflected variola-specific sequences or open reading frame divergences for variant proteins, which are often truncated or elongated compared with their vaccinia counterparts.