The HIV-1 epidemic: low- to middle-income countries

Abstract

Low- to middle-income countries bear the overwhelming burden of the human immunodeficiency virus type 1 (HIV-1) epidemic in terms of the numbers of their citizens living with HIV/AIDS (acquired immunodeficiency syndrome), the high degrees of viral diversity often involving multiple HIV-1 clades circulating within their populations, and the social and economic factors that compromise current control measures. Distinct epidemics have emerged in different geographical areas. These epidemics differ in their severity, the population groups they affect, their associated risk behaviors, and the viral strains that drive them. In addition to inflicting great human cost, the high burden of HIV infection has a major impact on the social and economic development of many low- to middle-income countries. Furthermore, the high degrees of viral diversity associated with multiclade HIV epidemics impacts viral diagnosis and pathogenicity and treatment and poses daunting challenges for effective vaccine development.

Figure 1.

Estimated HIV prevalences in 2009 among adults aged 15–49 years old in sub-Saharan Africa, Asia, Eastern Europe, and Central Asia. (Source: UNAIDS.)

Figure 2.

Phylogenetic trees illustrating the diversity of HIV-1 in Africa, Asia, and Latin America with the number of sequences included within each phylogeny roughly proportional to the percentage of subtypes contributing to each epidemic (as described by Hemelaar et al. 2006). The southern African epidemic is illustrated separately from the rest of Africa. Each sequence in the African phylogenies represents 250,000 infections, each sequence in the Asian phylogeny represents 200,000 infections, and each sequence in the Latin American phylogeny represents 26,000 infections. HIV-1 gp160 sequences from Los Alamos HIV database were used (http://www.hiv.lanl.gov/) and branch-length scale is in expected nucleotide substitutions per site. The figure was generated by Nobubelo Ngandu, University of Cape Town.

Figure 3.

Regional distribution of HIV-1 subtypes and circulating recombinant forms in low- and middle-income countries. Regions comprising different countries are colored in different shades of gray. The size of the bar is proportional to the size of the epidemic (UNAIDS 2010) with the proportion of the subtypes contributing to each epidemic (as calculated by Hemelaar et al. 2006) illustrated as a percentage of the bar.

Figure 4.

Regional distribution of HIV-1 subtypes and recombinants in Asia. The data of Malaysia, Indonesia, Philippines, Pakistan, Central Asia (including Afghanistan, Kazakstan, and Uzbekistan), and West Asia (including Saudi Arabia, Iran, and Israel) are from the Los Alamos HIV databases (http://www.hiv.lanl.gov/). The data of China, Japan, India, Myanmar, Vietnam, and Thailand are from former studies in the region and estimates based on the unpublished data of research projects (Y Shao, pers. comm.).