Mobility of injection drug users and transmission of HIV

Using phylogenetic analysis to trace HIV-1 migration among western European injecting drug users seroconverting from 1984 to 1997

OBJECTIVE

To reconstruct the epidemiological relationships of the HIV epidemics among injecting drug users (IDU) in western Europe.

METHODS

HIV env V3 sequences of and epidemiological data were obtained from 145 IDU who seroconverted in three sequential periods: 1984-1988, 1989-1992 and 1993-1997. The sequences were phylogenetically analysed and examined for signature patterns characteristic of northern European IDU, including the conserved GGC codon in the V3 loop.

RESULTS

Subpopulations of genetically related HIV strains were observed in Italy, France, Scotland and Spain, in contrast to the Netherlands, Austria and Switzerland. This difference between the two groups of countries suggests that the HIV epidemics amongst IDU in the latter group was caused by multiple virus introductions. In Edinburgh and the surrounding area, most IDU were infected with the same GGC strain over the 12-year study period. The epidemic among IDU in north-western Europe started with GGC viruses, whereas in south-western Europe non-GGC viruses predominated. This geographical separation has faded during the course of the epidemic, most likely because of virus exchange among IDU populations.

The epidemiology of HIV infection in Edinburgh related to the injecting of drugs: an historical perspective and new insight regarding the past incidence of HIV infection derived from retrospective HIV antibody testing of stored samples of serum

The pattern of sudden explosive outbreaks of HIV infection among drug users has been seen in several countries but is as yet incompletely understood. The epidemic of injecting drugs in Edinburgh was associated with at least four overlapping epidemics of blood-borne viruses (hepatitis B, C, D and HIV). Only hepatitis B was initially recognized, being followed by HIV and latterly hepatitis C. Retrospective HIV testing of stored samples of serum from clinically diagnosed patients with HIV has allowed the HIV epidemic to be delineated and more accurate seroconversion dates identified for most of the patients. There is evidence to suggest that the explosive drug-related Edinburgh HIV epidemic may have been self-terminating and that the epidemic in male drug users preceded that in female drug users by around 3 months. We suggest that the self-terminating nature of this epidemic may have been related to changes in drug injecting behaviour or to varying infectivity of the virus. This latter possibility should be explored in future studies of HIV transmission.