**4. Recombinant circulating forms and distribution pattern**

observed amongst men [27] (Figure 3). The prevalent rates amongst MSM are also recorded to increase in the order, Hispanic MSM (6,700), black MSM (10,600), and white MSC being the highest (11,200) [27]. Up to 16% of total HIV reported cases are due to intravenous drug users (IDUs) in which they represent 8% of new cases [28]. Similarly, Europe has a high number of HIV occurrences from MSM [29]. It could be observed that in high income countries HIV epidemics is highly associated with MEM sexual networks [30, 31,32] while heterosexual

The data shows the prevalence based on 2013 United Nations Office on Drugs and Crime data from the annual report questionnaire and national Government reports, 2013 UNAIDS report and CDC publications. Note: IDUs stands for

Since both heterosexual and homosexual behaviour is a potent factor for increased HIV transmission rate, exploring the dynamics of this mode perhaps could be a sure way of providing and discovering a lasting HIV treatment option and drug design. A number of HIV epidemic models have emerged, particularly the modes of transmission (MOT) model recommended by the Joint United Nations Programme on HIV/AIDS (UNAIDS) [36,37]. The MOT model as developed in 2002 aims to identify persons at risk of HIV infection [38] with subsequent prevention policies and programmes [39]. This model was recommended for country-wide studies in the year 2008 as part of a synthesis process supported by UNAIDS and the World Bank Global HIV/AIDS Monitoring and Evaluation Team [40], with emphasis on local content and immediate environment prevailing circumstances. The MOT model

**Figure 3.** Regional distribution of HIV routes of transmission in HIV positive population

contacts prevail in low income regions [33,34,35] (Figure 3).

6 Trends in Basic and Therapeutic Options in HIV Infection - Towards a Functional Cure

injecting drug users.

**3.2. Exploring transmission models**

The capacity of HIV to exhibit a unique high genetic variability has posed a major challenge to its treatment [42]. The genetic diversity is also attributed to a high error rate of the HIV genome during transcriptase reaction and also high genetic recombination rate [43].

Recombination is defined as the process whereby various subtypes or strains of the HIV shuffle their genomic characteristics to form an entirely new strain. This recombination tactic, a system of alteration of the HIV genetic constitution, is mostly common with the HIV subtype-1 (HIV-1) and it is commonly called new circulating recombinant forms (CRFs) (Table 1). There also exists the HIV subtype-2 (HIV-2), which is relatively less pathogenic in comparison to HIV-1 [44]. The occurrence of CRF is closely linked to the dynamism of the HIV infection and epidemic and obviously to failure of most specific therapeutic target in eliminating the virus [45-47]. The study of the distribution pattern of the various subtypes is therefore highly crucial for effective HIV management especially in endemic regions of the world. Recombination occurs at a very rapid rate estimated to be in the order of 2.8 cross-over per genome per cycle [48]. Recombi‐ nation events between subtypes lead not only to an ever increasing diversity of the HIV strains [49] but also presents astonishing scenarios of emerging strains with resistance to the common antiviral drugs [50,51]. The numbers of CRFs are increasing astronomically global, partly because of the emergence of recombinants of the various subtypes in various local epidemio‐ logical regions [46]. There has also been a correlation between the emergence of divergent subtypes in a population and the teeming occurrence of disease cases. For example, in Cameroon, the number of newly infected individuals increased from 8,596 to 10,625 between 2006 and 2007 as the number of recombinant subtypes increases in the studied population [47]. Criteria set to define a new subtype, sub-subtype, or CRF include having the representative strain identified in at least three individuals who have no direct epidemiological relationship. Three full-length genomic sequences are required but two complete genomes together with partial sequences of a third strain could also define a new subtype, sub-subtype, or CRF. CRFs are derived from recombination between viruses of different subtypes which are each given a number. CRF12\_BF, for example, is a recombination between subtypes B and F.


Spatiotemporal Dynamics of HIV Distribution Pattern and Application of Indigenous Bioresources and Microbicides… http://dx.doi.org/10.5772/61000 9


\* Recombine only with A, G, H, K, U, CPX=complex recombination of several subtypes (ADG)

**Table 1.** HIV Classification and global CRFs
