THE MOLECULAR EPIDEMIOLOGY OF HUMAN-IMMUNODEFICIENCY-VIRUS TYPE-1 IN 6 CITIES IN BRITAIN AND IRELAND

We have sequenced the p17 coding regions of the gag gene from 211 pati ents infected either through injecting drug use (IDU) or by sexual int ercourse between men from six cities in Scotland, N. England, N. Irela nd, and the Republic of Ireland. All sequences were of subtype 5. Phyl ogenetic analysis revealed substantial heterogeneity in the sequences from homosexual men. In contrast, sequence from over 80% of IDUs forme d a relatively tight cluster, distinct both from those of published is olates and of the gay men. There was no large-scale clustering of sequ ences by city in either risk group, although a number of close associa tions between pairs of individuals were observed. From the known date of the HIV-1 epidemic among IDUs in Edinburgh, the rate of sequence di vergence at synonymous sites is estimated to be about 0.8%. On this ba sis we estimate the date of divergence of the sequences among homosexu al men to be about 1975, which may correspond to the origin of the B s ubtype epidemic. (C) 1997 Academic Press.