Studies, including some in STIs journal, have mapped the geographical distribution of HIV types, subtypes, recombinant variants (CRF): see: (Middle East) STIs/Mumtaz&Abu Raddad; (Sub-saharan Africa) STI blogs/Tatem&Salemi. Such work has potential importance for our understanding of the evolution of HIV resistance, and also for the identification and targeting of established and nascent epidemics among core risk groups in a population.
A recent paper (Palm&Medstrand) takes this kind of research in a less familiar direction, by examining the association between subgroup and rate of disease progression in Guinea-Bissau. Should certain subgroups or recombinant variants prove to be associated with much swifter disease progression, this knowledge would be relevant to the management of patients (monitoring and testing intervals), as well as being essential to our understanding of the scale of the HIV problem in the area concerned and its implications for planning a response.
Problems for earlier research, according to these authors, include obtaining estimated dates of sero-conversion, and a tendency towards “broad brush” comparisons between groups combining a diversity of subgroups and recombinant variants. Palm & Medstrand had data for seroconversion as well as disease progression from a longitudinal cohort of police officers in Guinea-Bissau, including 225 treatment-naive HIV-1 seroincident individuals, going back to 1990 and continuing, with the exception of the two-year interval (1998-9) of the civil war, to the introduction of the national treatment program in 2005. They analyse disease progression (time from sero-conversion to AIDS and AIDS-related death) for each subtype/CRF independently.
The overall epidemiological picture for Guinea-Bissau has undergone a transformation since the nineties of the last century (STIs/Mansson&Norrgren). The 147 individual samples, for which sequencing and assignment of subgroup was possible, demonstrated a distribution of HIV-1 subtype/CRF that resembled previous recent estimates for Guinea-Bissau, including, almost exclusively: subtype A3 (29%), CRF 02_AG (53%), plus a recombinant of these two, A3/02 (13%). Compared with A3 (which showed the slowest disease progression), CRF02_AG was associated with a risk ratio for progression to AIDS and AIDS-related death of 1.4 and 2.2, respectively; A3/02 with a risk ratio of 2.6 and 2.9, respectively.
Recombinant variant A3/02 shows the fastest progression rate reported to date. Given the three-fold difference in progression rate between HIV-1 A-like subtypes/CRFs, the authors stress the importance of determining the HIV-1 subtype of infected individuals.