Human monkeypox and smallpox viruses: genomic comparison

Monkeypox virus (MPV) causes a human disease which resembles smallpox but w ith a lower person-to-person transmission rate. To determine the genetic re lationship between the orthopoxviruses causing these two diseases, we seque nced the 197-kb genome of MPV isolated from a patient during a large human monkeypox outbreak in Zaire in 1996. The nucleotide sequence within the cen tral region of the MPV genome, which encodes essential enzymes and structur al proteins, was 96.3% identical with that of variola (smallpox) virus (VAR ). In contrast, there were considerable differences between MPV and VAR in the regions encoding virulence and host-range factors near the ends of the genome. Our data indicate that MPV is not the direct ancestor of VAR and is unlikely to naturally acquire all properties of VAR. (C) 2001 Published by Elsevier Science B.V. on behalf of the Federation of European Biochemical Societies.