Background Human Immunodeficiency Virus Type I (HIV-1) is characterised by a high genetic variability. The distribution of HIV-1 subtypes in a population can help track transmission patterns and the evolution of the epidemic. The Middle East and North Africa (MENA) continues to be perceived as a region with limited HIV epidemiological data, but recent research indicates that nascent HIV epidemics appear to be emerging among high-risk groups including injecting drug users (IDUs), men who have sex with men (MSM), and female sex workers. The objective of this work was to review all evidence on HIV-1 subtype distribution in MENA where there remains several gaps in our understanding of the HIV epidemic.

Methods A comprehensive systematic review of all HIV-1 molecular epidemiology data in MENA was undertaken. Sources of data included (1) PubMed using a strategy with both free text and MeSH headings, (2) country-level reports and database including governmental and non-governmental organisations publications, and (3) international organisations reports and databases.

Results In several countries such as in Lebanon, Saudi Arabia, and Yemen, a very diverse distribution of HIV-1 subtypes was observed reflecting principally travel-related exogenous exposures. A trend of a dominant HIV-1 subtype was observed in few other settings and was often linked to HIV transmission within specific high-risk core groups such as subtype A and CRF35_AD among IDUs in Afghanistan, Iran, and Pakistan; and subtype C in heterosexual commercial sex networks in Djibouti and Somalia. Subtype B was predominant in Northern Algeria, Tunisia, and Morocco, but this appeared to reflect a mix of indigenous endemic transmission and exogenous exposures of West European and North American origin.

Conclusions Multiple introductions of HIV-1 variants due to exogenous exposures of nationals seemed common to all MENA countries, as observed from the high diversity in subtypes or the high genetic divergence among any specific subtype even if predominant. This is in part a reflection of the high population mobility in MENA. In several countries though, epidemic-type clustering of specific subtypes suggests established or nascent HIV epidemics among classical core risk groups for HIV infection. With overall weak surveillance systems in MENA, molecular investigations could help identify the emergence of hidden epidemics among high-risk groups. HIV prevention efforts in MENA must be prioritised for these groups.